So it looks like you're building control. For a 60 card control deck, the creature package feels a bit heavy. Maybe drop the nantuko shades as you'll have other ways of closing out the game. If you want to keep 2 cmc creatures you might look at Yarok's Fenlurker. Raven's crime while strong is not a card you really need more than 1 of. I'd drop to 1 copy and, if you want more help finding it, look at running an entomb package. Likewise, 4x necropotence is probably a bit extreme. Demonic Consultation is obviously an amazing card, but I'm not sure I like it without a combo win in the deck. Maybe drop the sinkholes for some space?
One card you might look at if you like the heavy mana life gain style is Bolas's Citadel. With it you could play stuff like Corrupt or Tendrils of Agony as a way to get through your deck on minimal mana. Having it in play with Necropotence is also good because if you hit a card you don't want necro can exile it. Tutors you're missing are (ignoring price):
4 vampire nighthawk
4 desecration demon
3 necropotence
1 demonic tutor
1 vampiric tutor
1 demonic consultation
1 yawgmoth's will
4 hymn to tourach
4 inquisition of kozilek
1 crucible of worlds
1 raven's crime
1 mind twist
2 ivory tower
1 mox jet
2 cabal coffers
1 reliquary tower
4 strip mine
1 urborg, tomb of yawgmoth
4 dark ritual
One card you might look at if you like the heavy mana life gain style is Bolas's Citadel. With it you could play stuff like Corrupt or Tendrils of Agony as a way to get through your deck on minimal mana. Having it in play with Necropotence is also good because if you hit a card you don't want necro can exile it. Tutors you're missing are (ignoring price):