in those kinds of one-way decks, you definitely need at least 4 copies of
thoughtseize or
inquisition. Plus, if you want some good removal, i would consider
feast of blood.
Guul draz assassin is another strong vamp one drop who also scales good into the late because he also functions as a good mana sink.
i don't know how much more lategame is needed in this deck, but maybe you could consider one or two phyrexian arenas, because even just on of those in play provides enough card draw for the rest of the game.