While I enjoy your feedback, it wouldn't be that hard to code at all, really. Whenever a creature dies, just add a variable called "bloodlust" and have it +=1;. Then convert Bloodlust into a regional variable by doing something in the actual vampires code, like VampireAttack = bloodlust. Then under the If string to have the vampire attack, add "if VampireAttack > 0", and have VampireAttack subtract one each time the vampire attacked.
And I get that that you'd have to kill two creatures to make this effective, but it's really not all that hard to kill two creatures. Fire, Death, and Entropy, and Dark itself all have kill spells/kill creatures, and they're the most common elements paired with death. It would give the card an opportunity to kick major butt.