Lol. I've had a Sampire with GM SS for years, and it's pretty damn powerful. Vampire Form by itself, only gives 25% Life Leech or so. Curse Weapon with GM Necro/GM SS, gives 50% Life Leech, and it stacks additively with Vamp Form, for 75% Life Leech. Can go from almost dead to full health in a single hard AI hit. I can also go into Wraith Form and cast Curse Wep, for both Mana Leech and 50% Life Leech, non stop AI/WW spam (so long as the victims have Mana remaining).
If i can't reach a monster with my melee (like when Fire Daemons sit over lava), i can still kill them with spells like EO+Corpse Skin, Strangle then Poison Strike spam, all the while leeching Mana back with Wraith Form, and if i take damage, i can use SS to heal myself. It's essentially a build that can switch between Sampire or Whammy with a single transformation spell.