I remember that contests with scoring for using certain heroes in Arena and/or Coli were more common way back when, well before Challenger leagues introduced special rules that further limited the number of heroes that could be used. And even without those rules, people would complain about those contests, because some heroes would be outdated and useless and others would be too new for most players to have leveled up.
When the scoring was for using heroes in City Watch, those same problems applied, but at least people could hire a merc and score points that way. Of course, nowadays, with people needing to maximize their red skill chip earnings from Epic City Watch in order to have a chance at keeping more than one or two skills at max level, being forced to use certain heroes for City Watch is arguably worse than being forced to do so for PvP.
That leaves Surge, where players have the best chance to score points with underdeveloped heroes and where mercs can be of the greatest use in helping score points. But that brings up a different problem, namely how to keep players from hiring all the good contest mercs for themselves and leaving their guildmates high and dry. I’d be perfectly fine with points not being awarded for hired mercs, but I suspect I’m in a very small minority.
I’m not really sure if it’s still possible to design a contest that awards points for using certain heroes and have it appeal to the majority of players. I suppose the next best thing is a contest like this one, where (as Pipsqueak pointed out) the points one can earn for using those heroes hardly matters at all. It’s a shame, really, because it would be nice to have more variety in these contests.