The amount of health you can get with a Vampire is ridiculously high. For fun I tried Havendale Bridge for a double Sensation stone, I also got Alchemist Scroll at level 3, and used JJ for an extra 75 health. I reached 580 health
and I think 650+ is doable with extra gold and Pactmaker on top of that (Spirit Pact is pretty good considering you get an extra 10 health every 4 conversions, think about potions, spoons, et al...).
I defeated Demonic Library without Dracul, using JJ only, and no spells besides WEYTWUT (I converted everything). So it's all about maxing life, and a good management of blood pools and low level monsters/tanks for some lifesteal regen (take 2 Blood Hunger early, 3 if you can desecrate freely).
A good way to use exploration as a ressource is if you have, say, meat men. Lifesteal all of them without killing, explore a bit, and come back at fresh meat. It is known that Vampires like to keep their victims alive.
And try to use blood pools only when it's for killing +2 or above monsters.