Grats on vampirism, but it's really useless until it can be leveled. Due to the experience gains needed you won't get the more useful skills until rank 4+ and some of the better ones at 6+. Fortunately the fire damage debuff has been nerfed so its not that bad anymore. I remember the 40% and it was very, very hard dealing with just a couple of Banekin at times.

I wager that you won't max out on rank 10 vampire until about level 42-45 or so.

Lastly, vampirism is only really (kinda) useful for Nightblades. Both my NB's are vampires primarily for the synergies of abilities across skill lines. My sorcerer was originally my first vampire but I cured her after realizing that the skill line offered nothing whatsoever and actually worked against sorcerer-based synergies.

To each their own, however.