I have my theories.
First we should analyse vampire feeding. Do they kill the prey or take a little from, maybe, 2 or 3 adult humans to be sated? How much time can they be without feeding? what consequences do they have if they don't feed? (Do they decay/wither away, do they go feral and attack everything that moves)
Some hunters hunt for survival, others for revenge, others for religious fanatism.
If we could reason with vampires they could be very useful for humanity. Defense, knowledge and with some experimentation in the middle, a way to prolong human lifespan.
Sorry too much Vampire the Masquerade