Well, if you like how tree works and it's been useful for you, go for it. It's EDH and there should never be two decks equal in everything. Every player is different. I think it's Tree good, but is not for me.
As for
Necropotence, I think it's very important, any "Pay 1 life" is critical here, so you can control perfectly the suicide. Also the effect is very good and gives 3 devotion. I can see people cutting it out because of the effect itself, but it's my pet card and ai only cut it when is bad (not enough black lands, discard or graveyard deck, etc).