I’m on Server 22, Arena level Platinum IV. And I’ve been there for weeks.
It’s impossible to progress. My top five heroes are ~310K power, the Arena ranges from 250K to 350K, and we’re all levelling up at roughly the same rate. Every now and then I hit number 1, then next morning I’m back down to 43rd. There’s just no way anyone can stay in the top 5, so everyone is stuck. We’ll never get to Challengers. Right now I’m not even playing Arena until I get demoted back down to III, just for a change of scenery.