here is how I play a vampire:
When you get to the endgame with enough lowlevel monsters left, the boss is a piece of cake. So you need to kill as few as possible mobs to gain a high level without wasting your levelup full heals. The item I use for that is the Balanced Dagger (one of my favourite preps, although noone seems to like it
). Another important prep is "More glyphs", because of the 120 threshold... it nearly never matters and you have a higher chance on a GETINDARE.
Some important things about Lifeleech: You get one life per level per stack of lifeleech you have. But this is caped at your damage dealt (AFTER enemy resists) and the enemy HP. It also is given back to you AFTER the enemy attack, so if you die first, it does not help you. This leads to a wrong calculation on the HP bars! It may seem like you can hit 4 hits, but you can do only one... A perfect glyph for lifeleech is GETINDARE, because if you first strike, the enemy doesnt strike back when hes dead, giving you all enemy HP left as your own HP. Dodge is even stronger, giving you a FULL attack worth of life (capped by your lifeleech) with no retaliation.
Playstyle: Scout for the monsters on your level with the most damage to kill, because it is not useful for lifeleech. If you find a glyph you don´t like (lemisee for example is worthless) convert it instantly. Buy items that give lifeleech, give resists or increase base attack/attack bonus. Don´t rely on mana items, the vamp is a crappy spellcaster. When you have a few DINGs, you can start to use your low level popcorn with low attack values to milk for life. Start with one to get overheal, attack a high level enemy, attack other popcorn to fully heal, attack the enemy again, getindare dead. If that reliabally works, you can convert the balanced dagger for that extra lifeleech, because you wont use it anymore.
Dont use bloodpools, only for that emergency last bit of health to kill the enemy. When you get to the boss with some lvl 6 meatmen or something like that, you can just switch between attacking the boss and the meatmen, dont caring about any ability the boss might have.
This way I managed to kill Vicious Horatio, so it should be appliable to low level dungeons aswell