Disclaimer: This Guide will always be in progress & based on my learnings & understanding. I might be wrong on few points which you can correct & give suggestions. Based on Servel Level 160 & R5
My comprehensive Mods & Mods Upgrades Guides for heroes can be found here. All suggestions are welcome. If you want to read in Google Doc, here is the Guide Link
Important Stats

Evasion: Evasion gives heroes a chance to avoid enemy disables. Each point of Evasion above the enemy’s skill level increases your chances of avoiding a disable by 1%, up to 90%. If a disable is avoided, any other effects on the skill still resolve.
I will explain this by taking an example, now let’s see Evasion of Cat at R5 level 160 with a max badge is 228, now you have seen that Minnie’s charm or Kristoff freeze doesn’t work on Cat, the reason is high Evasion. So, as per the definition in order to charm the Cat, you need to level up Minnie’s Green Skill.
As per definition 1 skill level above hero level will increase your chance of disabling the cat is 1%.
So, 228 ( evasion )  160 ( skill level ) = 68 level. So, in order to charm the cat by 90 %, you need to bring that skill level to 228, which means +68 level ( can be done by using mod upgrades ) 
Tenacity: Tenacity reduces the length of stuns and disables a hero receives. Each point of Tenacity above the enemy’s skill level reduces the length of stun or disable by 1% up to a max of 90% reduction.
So, it works the same way as evasion, you need to increase your skill level to minimize the tenacity stat, lower the tenacity stat & your skill will work more time.
Max has high Tenacity so in order to freeze Maximus for more time you need Kristoff’s blue skill to as near as his Tenacity Sata 
Skill Power: Skill Power increases the damage that some, but not all, Skills do.

Skills displaying a Blue Damage Number do more damage as Skill Power Increases. The amount of the increase varies by Skill.

Skills displaying an Orange Damage Number do more damage as Basic Damage Increases.

Skills displaying a Green Damage Number do more damage as the Level of that Skill Increases.
So, always keep in mind these colors while equipping mods, if you see orange damage in skills, you need to increase basic damage that means you need to Equip BD mod.
Important Tips
 Shield mod upgrade will help in gain hardy at the start of the wave if paired up with Baymax
Timon & Pumba  170 R7
Summary
Stats
 Armor  46507
 Reality  65122
 Normal Crit  226
This pair is counter to many toons nowadays & their stitch disc makes them really good. Well, they do fantastic damage & they don’t have fantastic crit stat, so yeah no need to upgrade normal crit.
Also, no orange damage, so no need for BD mod. Now, with their green skill, they keep the team alive against toons who do normal damage plus they provide healing over time also by Hakuna Matata.
So, First & Second Mod should be SP mod with Green Skill upgrade to give the team an insane amount of armor & healing at the start of wave & also in between the fight when they reach 50% of HP.
Now, let’s come again on BD mod, no need to increase basic damage as no orange damage, now their skill doesn’t depends on cooldown except Blue Skill, instead of this more the time they survive in battle more they are useful because of Red Skill as whenever a buff is removed or stolen from them or their ally, Hakuna Matata again activates.
So, to keep them alive provide rest 2 mod as HP mod with Reality Upgrade as they get armor from green skill.
Mod Matrix
Skill Power  Skill Power  HP  HP 

Green Skill +40  Green Skill +40  Reality  Reality 
Summary
Stats
 Armor  69489
 Reality  69117
 Reality Negation  225
 Normal Crit  212
 Fantastic Crit  237
Elsa was in Freeze meta for a long time, but now as the game progresses due to hardy, evasion & tenacity, she is becoming less useful, but you can make her good enough if you can mod her up properly & pair her up with good toons.
Now, the longer she can survive, longer she can freeze the toons, which can be done by pairing her with slinky or other toons who can provide her Armor & Reality.
Ian Lightfoot  170 R7
Summary
Stats
 Armor  42729
 Reality  94051
 Normal Crit  239
 Fantastic Crit  199
Ian’s red skill provides fantastic crit stat, so at 170 it will become +95, so it will be 294. He will crit without upgrading BD mods.
Now, see Ian is a good counter to Mulan, Louie & he can be used in various setups & his mods totally depend on your use. Personally, I use him to counter Mulan, Louie & to shrink OP toons with high evasion. For this, I have given Two SP Mods with Blue skill upgrade which helps me in shrinking toons.
Ian is also a good counter to Max by continuously knocking him back & Max has good HP, so you have to keep Ian alive. So, yeah an Armor Upgrade is required because red skill already provides him Reality.
One good thing is his red skill which gives Fan Crit & you need only +76 in order to have a 100% chance of Super Crit & for this you will need 3 Fan Crit upgrades on BD mods
His green skill is also a nuke & just keep him alive for 4 seconds & with green, he can wipe out at least 3 toons if you give him 4 Green Skill mods as he will crit that damage.
Mod Matrix
Ian  The Damager ( if you have enough resources)
Skill Power  Skill Power  Skill Power  Skill Power 

Green Skill +40  Green Skill +40  Green Skill +40  Green Skill +40 
An alternate version of is this if you want to shrink cat, the horse just give Two Blue Skill & Two Green Skill
Ian  Survivor
HP  Skill Power  Skill Power  Skill Power 

Armor  Blue Skill +40  Blue Skill +40  Green Skill +40 
Ian  Another version of damager if you have resources
Basic Damage  Basic Damage  Basic Damage  Basic Damage/ SP 

Fan Crit +32  Fan Crit +32  Fan Crit +12  Attack / Green +40 
another version if you are low on resources +24,+24,+12 & +12
Cheshire Cat
Summary
Stats
 Armor  18231
 Reality  100018
 Normal Crit  183
 Fantastic Crit  251
 Evasion  228
First Mod should be definitely Basic Damage & attached Fantastic Crit Upgrade, as Cat’s fantastic crit is at 251 once all badges maxed on S21, so there is 91% chance of crit. With the mod upgrade, raise this stat to at least 260 ( more the better ) so that cat can have a 100% chance of doing fantastic crit, DO NOT USE NORMAL CRIT UPGRADE
Second Mod should be HP mod with armor upgrade as Cat’s HP is high & armor is quite low so definitely you need to add provide ARMOR to keep CAT alive in battle, No need for reality upgrade
Rest two mods now will depend on the team you are facing, so let’s assume the opponent team have minnie, baymax, kristoff who have modded their skill & disables can’t be evaded by Cat, cat’s evasion is 228, So if Minnie’s green skill modded & maxed it will be at 230 level, then Cat can’t evade charm or freeze in case of baymax (olaf disk), So, trigger Head Toss before Minnie’s charm or Kristoff ice slide or similar other skills & for faster Head Toss, add attack speed mod upgrade as 3rd Upgrade.
Now, the last mod should be SKILL Mod with Green Skill Upgrade ( no need of another skill upgrade) )to increase the damage of Head Toss, Now let’s say you don’t have sufficient mod upgrades for fantastic crit or attack speed, you can attach BD mod and attached Crit or speed boost as per your requirement. You can get 10% speed by using two BD damage and using only 30 upgrade pieces else you have to use 55 pieces on one BD.
So my suggestion will be
Balanced Cat
Basic Damage  Healing Power  Skill Power  Basic Damage 

Fantastic Crit  Armor Only  Head Toss +40  Attack Speed +10 
High Damage Cat
Basic Damage  Healing Power  Skill Power  Skill Power 

Fantastic Crit  Armor Only  Head Toss +40  Head Toss +40 
The interesting thing is if you will see fantastic crit it is already very high 251 & you need this stat at 365 for Super Crit, which means 3x damage from white & green skill
So, you can also go with all 4 BD Mods with Fan. Crit Upgrade & reach up to 365 easily to super crit
Faster Cat
Basic Damage  Healing Power  Basic Damage  Basic Damage 

Fantastic Crit  Armor Only  Attack Speed +10  Attack Speed +10 
Disgust
Summary
Stats
 Armor  28537
 Reality  54311
 Normal Crit  199
 Fantastic Crit  230
Disgust is OP because of her green skill damage at 160 it is 405128 & at 240 level it is 1701954. The initial cooldown is 4 seconds
First Mod should be HP mod with armor upgrade as Disgust’s HP is high & armor is low so definitely, you need to add provide ARMOR, the reality is relatively higher, So, I would suggest pairing her with a toon who can provide reality just to be on the safe side.
Now with disgust it is quite interesting as to save from minnies charm or freeze from wellmoded skill toon, needs to activate her Green skill faster, so you need attack mod but the interesting thing is not many players have perfectly modded skills.
So, just do a fantastic crit upgrade as it is low for her  230 & for 100% crit chance need this stat at 260, so Second Mod will be BD with Fantastic Crit Upgrade.
Third & Fourth Mod will be skill power mod with green skill upgrade to deal an insane amount of damage in the first 4 seconds
So my suggestion will be
Disgust
Basic Damage  Healing Power  Skill Power  Skill Power 

Fantastic Crit  Armor Only  Green +40  Green +40 
Damage Booster Disgust
Basic Damage  Skill Power  Skill Power  Skill Power 

Fantastic Crit  Green +40  Green +40  Green +40 
You can also give One Attack speed to launch before Cat.
Angel (In Progress)
Summary
Stats
 Armor  38901
 Reality  64314
 Normal Crit  194
Now at a present level game if you see most of the heroes do fantastic damage, gone are the days of mulan, so you should build reality mods on toons but you never know about new toons.
Angel, have low armor & high reality once badges are maxed.
So First Mod will be HP with armor upgrade to save from normal damage hitters.
Second Mod will be BD , now none of the skills do normal damage so no need to put normal crit upgrade. One good point is that angel’s basic damage is good & enhanced by skills & disc & all basic damage is normal damage unless mentioned clearly. So, you can go with crit upgrade but I think it will be a waste of resources as getting upgrades is difficult in game also. Best shot is to give Attack Speed upgrade to mod, it will give attack boost.
Now angel’s charms is perfect so it can be evaded or reduced, so no need to work on Green Skill, I would definitely give purple mod upgrade if you are planning to use angel in silence team as it will boost her Basic Damage, at 230 level she gains 42120 BD per silence & with attack speed boost she can do good damage with basic attack.
Third Mod will be Skill Mod with Purple Mod Upgrade only if you are using angel in Silence Team
Fourth Mod will be BD mod to Spam Basic Bamage & in this case go for Attack Speed upgrade
If you don’t want to use Attack Speed, then use NORMAL CRIT BUT USE ON BOTH MODS to reach 260 by using less upgrade pieces.
Silence Team
Basic Damage  Basic Damage  Skill Power  HP 

Nor. Crit or Attack  Should be Same  Purple +40  Armor 
Normal Team ( still in progress  need suggestions )
Belle
Summary
Stats
 Armor  39534
 Reality  32502
 Normal Crit  252
 Evasion  273
 Conservation  30%
First Mod should be BD with normal crit mod upgrade, belle have already good stat on Normal Crit so definitely normal crit, so need only +8 to have a 100% chance of normal crit damage. Also, it will increase basic damage which will help blue skill as Orange Damage can be increased by increasing basic damage of that toon.
So Second Mod must be a skill power mod with a blue skill upgrade as it does normal damage.
Now, as long as Belle will be alive in battle, she can provide hardy with every basic attack so go Third Mod should be HP mod with Reality Mod as the current game is filled with OP toons with fantastic damage.
Belle’s Purple Skill can increase her speed up to 75% & in the hardy team, it can be achieved from the start of the battle & with every 3rd basic attack Belle gives hardy to ally so faster the belle more hardy & other toons can be spammed, Fourth Mod will be BD with attack speed upgrade, BD will increase blue skill damage also.
Mod Matrix
Basic Damage  Basic Damage  Skill Power  HP 

Nor. Crit  Attack Speed  Blue  Reality 
Note: Use toons who can give armor to Belle or in the later game when Normal damage OP toons will come, give armor mod upgrade
Slinky  165 R6
Summary
Stats
 Armor  68240
 Reality  150662
 Normal Crit  189
Slinky does only fantastic damage so normal crit doesn’t make sense here & the role of the slinky is to keep the team alive by spamming shields.
His skills & powerline disc provide a good amount of reality to himself & to allies when shielded. So, his reality will always be enough for him.
Therefore, First Mod should be HP mod with Armor Upgrade to save from normal damage, I know dog already has a good amount of armor but the more the better for the team.
Second Mod, should be again HP mod with Shield Upgrade, so that dog can get instantly more armor & reality from purple skill. This can also be spammed by Baymax red skill as well or some other toon as well  I will update later on this.
Now, slinky will be great for a stall team in arena & War, so just give him as much as reality & armor from purple skill, so for a good stall team Third & Fourth Mod should be Skill power mod with Purple Skill Upgrade
Mod Matrix
HP  HP  Skill Power  Skill Power 

Armor  Shield  Purple +40  Purple +40 
Another Suggestion
HP  HP  Skill Power  Skill Power 

Armor  Shield  Purple +40  Blue +40 
Minnie Mouse  165 R6
Summary
Stats
 Armor  50929
 Reality  68448
 Normal Crit  220
Minnie’s green & purple skill is great but it fails on Cat, slinky basically toons with high evasion & high tenacity. See stats explanation at top of Guide.
King Louie  165 R6
Summary
Stats

Armor  55364

Reality  92816
Well KL has a good amount of reality & armor already ( armor on the lower side )
I would say all Four Mods to Skill Power Mods with Purple Skill Upgrade, no need of thinking much in his case.
If you still think of an armor upgrade as it is on the lower side, go with one HP Mod with armor piece & the rest 3 purple skill mods.
I would still suggest the 4 Purple skill mod as it will deal an insane amount of damage at the start of battle & it works really well with animal disc maxed. One banana will deal around 5664902 damage if all 4 mods are maxed +40. Source: wakkatu
Mod Matrix
Skill Power  Skill Power  Skill Power  Skill Power 

Purple +40  Purple +40  Purple +40  Purple +40 
Powerline  165 R6
Summary
Stats
 Armor  44616
 Reality  60389
 Reality Negation  221
 Normal Crit  202
 Fantastic Crit  204
 Evasion  230
Powerline can be used with two types of toons: Freeze ( Elsa, Olaf, Kristoff etc) or Blind ( Hank, Goofy, Jafar )or can be used with both heroes… So, the mod will depend on Team Type. So, First I will be giving suggestions that will work for both toon types.
Kristoff & Sven 165 R6
Summary
Stats
 Armor  72315
 Reality  73290
 Normal Crit  185
 Fantastic Crit  173
Kristoff was in meta for 34 months in the freeze team as he can freeze the entire team for 10 seconds with the blue team & it can be increased by 35% that means 13.5 seconds freeze from purple skill.
Davy Jones  170 R7
Summary
Stats
 Armor  44609
 Reality  107157
 Normal Crit  201
 Crit Damage  185
 Tenacity  215
So, this guy has a very good reality stat already with okayish armor. No need for reality mod here. But, with max red skill, his armor went up by a pretty decent number around the same as reality. So, no need for an armor mod as well.
The interesting thing is in white & green skill, his damage is Orange which means this will increase as basic damage increases, his normal crit is also good & need +69 to have 100% of Crit.
So, I would suggest giving him 3 BD mods which increase his basic damage & eventually his damage from white & green skill & go with normal crit on all 3 mods to reach 270 normal crit.
Now, his purple skill won’t get evaded by evasion as the curse is debuff & debuffs can’t be evaded so need to upgrade this skill for toons with high Evasion.
Also, Skill mods can’t increase his damage so avoid them here.
So, 4th Mod would be an interesting one, as giving purple & blue upgrades won’t make sense here, Green does damage & stun the attacker every 10 seconds which can be evaded or reduced.
I am not suggesting to put 4th mod as BD mod because at max 4 BD normal crit his stat will be 329 & for super crit ( 3x damage ) you need it at 370, so you have a 59% chance of 3x damage, if you are okay with RNG then you can go with 4 BD normal crit if you are low on the resource you can also go with 4 BD mod just to reach +69 distributed over 4 mods.
If you are able to reach +69 with 3 BD mod, then the Fourth mod should be Green Skill so that davy can also disable the toons
Mod Matrix
Balanced Davy  ( damage & disable the toon)
Basic Damage  Basic Damage  Basic Damage  Skill Power 

Normal Crit +24  Normal Crit +24  Normal Crit +24  Green +40 
Davy the Damager
Basic Damage  Basic Damage  Basic Damage  Basic Damage 

Normal Crit +32  Normal Crit +32  Normal Crit +32  Normal Crit +32 
Davy the Damager  if low on mod upgrade resources
Basic Damage  Basic Damage  Basic Damage  Basic Damage 

Normal Crit +24  Normal Crit +24  Normal Crit +12  Normal Crit +12 
The Manticore  170 R7
Summary
Stats
 Armor  55053
 Reality  77517
 Normal Crit  196
 Fantastic Crit  195
 Tenacity  265
Most people used her in the DOT team as she can do insane damage at the start of the battle. Her mushu disc is also interesting, it deals a good amount of fantastic damage.
Her skills also do fantastic damage except for white skill. So, yeah you are thinking right about the fantastic crit mod upgrade.
To crit, stat should be at 270, so she needs at least 270  195 = 75, interesting thing is at R8 with serverlevel 175 you only need 275  211 = 64.
Seeing this stat at R7 you definitely need 3 BD mod with Fan Crit Upgrade. I would suggest giving 3 BD mod with Fan Crit ( 24 + 24 + 24 )
BD Mod will increase Basic Damage & her white skill damage is Orange so it will increase that white damage also.
Now, let’s talk about survivability, her armor is good & if the red skill is maxed she will get additional armor +79147, so you need to work on reality stat.
The Fourth Mod should be HP mod with Reality Upgrade so that she can survive the battle. If she seems squishy pair her with Meg or some other toon who can help her being alive.
For those who don’t have resources, I will give another mod matrix below
Mod Matrix
The Manticore
Basic Damage  Basic Damage  Basic Damage  HP 

Normal Crit +24  Normal Crit +24  Normal Crit +24  Reality 
The Manticore  Another version increase damage by skill
Skill Power  Skill Power  Skill Power  HP 

Blue +40  Blue +40  Blue +40  Reality 
Blue will increase DOT damage, pair her up with hades (meg) for double damage at 5 star
Mulan  170 R7
Summary
Stats
 Armor  59013
 Reality  49606
 Armor Negation  191
 Normal Crit  246
 Crit Damage  216
 Evasion  244
Mulan was once too OP before Ian, Cat & Horse, well she still can be a very good damage dealer if modded & paired with toons who can provide an initial shield.
Her normal crit is quite good 246 & for Crit you need +24 crit, interesting thing is her purple skill, while shielded her crit increased by 100. So, in order to super crit, she needs her crit at 370.
So, First Mod should be HP Mod with starting shield ( also use her Bo Peep disc to increase shield HP ) & Second Mod should be BD mod with Normal Crit Upgrade, it will give Mulan Super Crit ( 246 + 24 + 100 = 370 ).
If you don’t want to give shield mod, then use her with instant shield givers like Animal(gonzo), Baymax, Slinky, or other toons.
The shield will also give attack speed to Mulan, so that’s one more benefit.
The Third Mod will be HP mod with Reality Upgrade as her reality stat is relatively lower.
Now, an interesting thing is that Mulan’s green skill target’s backline toons & stun them so it will be a direct counter for few toons like Kermit, Ian ( only if you are using Tron with Kevin 5 star disc which will remove reflect ), Evil Queen, Beaker, etc.
Mulan can crit the damage but can’t stun the toons always because of high evasion, so Fourth Mod should be Green Skill upgrade so that stun have better chances & more damage, also pair her with toons who can provide armor, reality, and skill power.
You can always avoid shield upgrades if you are going to use Animal, Baymax, etc. who can provide shields from the start.
Mod Matrix
Mulan (without shield giving toons)
Basic Damage  HP  HP  Skill Power 

Normal Crit +24  Shield  Reality  Green Skill +40 
Mulan (with shield giving toons)
Basic Damage  HP  Skill Power  Skill Power 

Normal Crit +24  Reality  Green Skill +40  Green Skill +40 
or you can also go with armor, but I use her with armor giving toons also fantastic damage toons are OP in the current game.
Maximus  170 R7
Summary
Stats

Armor  93943

Reality  70970

Normal Crit  212

Tenacity  254

Maximus normal crit number is decent & to Crit he needs 270  212 = +58

Damage from skills is Orange that means it will increase as basic damage increases

His HP is also quite good, it was highest once launched  tanky enough with good armor & reality stat
Summary
Stats
 Armor  59748
 Reality  92706
 Armor Negation  232
 Normal Crit  199
 Crit Damage  208
 Tenacity  10
Well, as I already mentioned in the stats explanation that not every hero needs mods like Barb. Instead of mods, his Tia disc makes him viable with DOT toons mainly normal damage toons like pleakley.
You can also pair him with Kim ( Jo ), which will slow down studied enemies. So, from the start of the fight, toons will get study unless they have counters like beaker.
Summary
Stats
 Armor  51940
 Reality  55112
 Reality Negation  215
 Normal Crit  215
 Fantastic Crit  177
 Crit Damage  180
 Evasion  255
Her evasion stat is great at this level, just mentioning. Well, her normal crit is decent but her skills do only fantastic damage so no need to work on normal crit.
Her Fantastic Crit is two low & you need hell of resources & damage is not Orange so no need of giving BD Mod
John Silver  170 R7
Summary
Stats
 Basic Damage  128668
 Armor  35730
 Reality  71697
 Normal Crit  206
 Tenacity  271
His skills work better if his HP is less so basically less the HP more damage he can do, a unique skill set.
So, the best way to use him to keep him alive with less HP, 2 ways of doing this is pairing him up with Megara ( make sure he should be at the front ), else pair him up with slinky to protect him from damage.
Hamm  170 R7
Summary
Stats
 Armor  121479
 Reality  61094
 Normal Crit  198
 Crit Damage  203
 Tenacity  242
Hamm is quite a tricky toon, as his white skill does True Damage, green & purple skill does not do damage.
His armor is already very good, but you need reality or another Tank on the team, so the First Mod should be HP mod with reality mod upgrade so that he can survive the battle at Front Position.
Now, his damage from Blue skill is good & also Orange, so you should give rest of the 3 BD mods with normal crit upgrade to do heavy damage by Crit which need +72 stat
Mod Matrix
Hamm  Another Tank in the team
Basic Damage  Basic Damage  Basic Damage  Basic Damage 

Normal Crit +24  Normal Crit +24  Normal Crit +12  Normal Crit +12 
If you have resources, max all mod & which will have 56% chance of super cri
Hamm  No other Tank in team
Basic Damage  Basic Damage  Basic Damage  HP 

Normal Crit +24  Normal Crit +24  Normal Crit +24  Reality 
Summary
Stats
 Armor 88399
 Reality  87445
 Armor Negation  10
 Reality Negation  224
 Normal Crit  192
 Fantastic Crit  241
 Crit Damage  253
After, refresh Tia is quite good & helpful in challenger also as she does many things like silence, charm, knockback, curse, gains energy with red skill so she synergizes with many toons like davy, yjma, magica and more, I will be covering this in team guides……