I'm in a similar situation as you. I think you should at least have around 10 maxed out 4* Champions and among those 10, you should cover each of these aspects of the game. Regeneration counterEvade counterPower control ChampionImmunity (bleed, poison, Coldsnap and incinerate)Strong nullify Champion Reliable questing Champion with lot of regen. Quake (she owns the game, a must have imo).If your 4* Champions cover all these things, you probably don't need to upgrade any more 4* Champions, focus on your 5*s.