I once considered removing the vampire's energy drain ability and replacing it with an at-will Vampiric Touch spell-like ability (CL equal to HD). That would certainly make it more like The Elder Scrolls.
Ok so vampires give 2 negative levels per slam, but don't get Temp HP. Could it be changed so they heal that way? the spell Vampire touch functions that way.
Actually, vampires do gain temporary hit points when they bestow negative energy levels:
Energy Drain description on PRD:
This attack saps a living opponent's vital energy and happens automatically when a melee or ranged attack hits. Each successful energy drain bestows one or more negative levels (the creature's description specifies how many). If an attack that includes an energy drain scores a critical hit, it bestows twice the listed number of negative levels. Unless otherwise specified in the creature's description, a draining creature gains 5 temporary hit points for each negative level it bestows on an opponent. These temporary hit points last for a maximum of 1 hour.
Also what about a spell that drains the blood right from an opponent? Or like in Skyrim where it is a Fireball AOE life Drain? Yes it sounds overpowered, but that really depends on the actual numbers involved.
There was 3.5 spell somewhere that acted like vampiric touch at range affecting a group of creatures. I think it was 5th or 6th level.
Using Kirth's method for determining spell level from existing spells, you can make a 20' radius burst vampiric touch as a 7th level spell and several lower level variations as well.