Either nerf doom or give everyone doom.
The power level doom has is so far beyond anything else in the game. He is in a class all his own. Literally it is the only answer for every bit of content now, and many people have him (including a level 41 with a 6* doom which is nice). Nerf doom or give everyone a 5* to even the playing field since a pity timer will not be implemented for crystals. If this upsets you, that is because you are abusing him, he is basically a cheat code.