I can't see the lifegain effect triggering much, even in Commander. You might be able to pay 11 mana, but 8 cards in your graveyard with different mana values? How often does that happen? Even a graveyard-centric deck will have to work to hit that threshold. And a graveyard-centric deck would probably rather keep those cards in the graveyard.Yeah, in Limited, it's "situationally useful" at best, but it is not likely to come up too often. In Commander, as @Charlaquin says, this is a major fat bomb.
The base recursion effect is decent, though.