Hello there... I know this is an old thread but Necropotence is one of my favorite cards as well as decks. I just wanted to chime in with my decklist, which is amazingly similar to what you guys have come up with.

Land

14x Swamp
3x Urborg, Tomb of Yawgmoth
3x Cabal Coffers
4x Strip Mine (Although I really like Mishra's Factory here too!)

4x Dark Rit
4x Demonic Consultation
4x Duress
4x Drain Life
4x Consume Spirit
4x Necropotence
4x Unmask
4x Spinning Darkness
4x Soul Spike

I really like the mana base...It makes casting a 20+ point drain effect completly possible...All I can say is that the deck is amazing, you usually always have necropotence out by turn three and once you stick the skull its over for whoever. The only problem I noticed with the deck is that a bad consult can f#$@ your couch so thats why i might like factories in there for an alternate win condition if you happen to remove all of yours. Anyway, if you guys check the thread ever tell me what ya's thinks!