Badass vamps deck, man! My two suggestions that come to mind were probably considered already, but Falkenrath Aristocrat provides another static sacrifice effect and is a pretty badass beatstick in her own right. Sorin, Grim Nemesis is also criminally underrated, in my opinion, and deserves more attention. If you give him a try, I bet you won't want to kick him out. He fits the flavor and strategy beautifully, if you ask me.

Np. Anyways, here's a link to my list, it may give you some ideas. Feedback and/or suggestions are appreciated. http://tappedout.net/mtg-decks/edgars-dega-vampires/

Fun reference to a very under-rated tabletop RPG. Deck looks very solid. I'd swap your mortify for vindicate if you have the ability to do so as vindicate is purely better.

may want Sorin, Lord of Innistrad and/or Sorin, Solemn Visitor over your current planeswalkers, as both make vampire tokens. Nameless Inversion and Crib Swap offer neat removal that nets you a token (as they are both vampire spells due to tribal changeling).

Skullclamp can replace some of the pay life to draw cards, as clamping a token is effectively kicker: draw 2 for vampire spells. Indulgent Aristocrat and Bloodline Keeper  ^Flip are solid tribal "lords"

and Gatekeeper of Malakir is amazing, but woefully forgotten. hope this helps!