On paper, it sounds like an excellent class, but in reality, it's crap IMO.
First I tried pvp'ing with it, and it's really bad... You'd have to start out with your Blood Thief and Crimson Shield combo, or else you die. The abilities take 33% and 20% from your TOTAL health, not your CURRENT health, which makes it really weak. The heal from Life drinker is minimum, even with lower health. Also in pvp you won't get that much mana since those shitheads who think they are pro keep running around. The heals you get from your combo are like, 12-20... really nothing if you compare it to the health costs. If you start out with both skills, you lose more than half your life, and healing it back goes way to slow. Also, this class doesn't do any decent amount of damage against someone in PVP. A fucking healer finished me off in PVP... (Did win from a lvl 23 though).
Then, I tried to solo a boss. I tried Kathool (/join deepchaos). I could easily take him down with necromancer so I tried him with blood titan. Blood titan is a far cry from the epicness that is necromancer. As I said the heals are minimum and the Blood Thief and Crimson Shield combo is not worth it if the monster does 150-600 damage each time. I came at like 1/4th of his health when I died. When I tried it with Lucky/wizard enchancements, it's utter crap. When I tried it with warrior, it became more decent.
Now I might have played Blood Titan the wrong way (probably), but to me, it is pretty bad. I'll try experimenting different combo's, but the Blood Thief and Crimson Shield combo is pretty bad...