Okay, power damage Doomsday can be seen as not viable, but he can work out amazingly well with a good team composition. There's not much to be said about how to play him, as he will play out as a normal Doomsday only with better damage over time and AoE. His jungle clear is pretty amazing, and that makes him an amazing jungler, able to get in, deal massive amounts of damage over time, and be the last one standing. When late game comes around, you want to combo your Burning Core with Berserk to get massive amounts of disintegration and DoT. He plays a lot like API, but with much better mobility. The cdr will help you run berserk and burning core much more often, making you an amazing asset to any team.