I don't think that Promise of Power is a solid card drawer (please correct me if I'm wrong). It seems to me that the casting cost is prohibitive. Perhaps you'd do better with Necropotence or Phyrexian Arena...
Do four (six with Promise of Power) creatures feel like enough threats to you? It seems slim to me.
I like Demonic Consultation better than Vampiric Tutor. You get the card in your hand now, not next draw. That's my thought.
Other than that... I don't really know. Hope that helps give you some insight.
The current decks I play against are very pretty creature/burn heavy so I worry about Necro because I can't draw if I am low on life.
As far as threats go, I figure to be able to kill most people with Spiritmoger or hopefully neuter and deck them with Haunting Echoes.
The way I see it, LD still suffers has the same problems it did a few years ago. It has gotten better but the main problems as I see them are spot removal and kill condition. I am really interested in hearing a variety of opinions that could help me better this deck and appreciate yours.