I have a vampire deck that is black and white too. (http://www.mtgvault.com/ViewDeck.aspx?DeckID=277862) I have a lot of luck with Sorin, Lord of Innistrad, I can see how the Quag vampires might help me out a lot. I'll have to throw some in. I find spells like Mortify and Unburial Rites are also handy in a couple situations.
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I like vampires, have a sweet deck myself. (http://www.mtgvault.com/ViewDeck.aspx?DeckID=277862) I think you could try to get ahold of dragonskull summits in place of evolving wilds. You main deck feels heavy, I drew a dozen hands and only got two or three that I liked. Maybe you could slim it down a little to speed things up.
Have you considered Mycosyncth Wells? they only cost two, then you sacrifice them right away and walk away with two basic lands in your hand.
Changed it since you last commented, its a little faster now, and hits a little harder. I rely less on little vampires and it seems to work better.