Has there been much happening to the Vampire at all, or are there simply too few people available (aka, they haven't unlocked them yet) to properly test out the three monster classes? Vampire in it's current state struggles, to varying degrees depending on the map/random stuffs, but I find he always struggles. But once you get past that point, pretty much everything from that point on is a cakewalk for Vampires. Simply put, he feels far too weak on earlier levels and too strong later on.
Sure, the alpha vampire was just silly overpowered. If he could get past the first level or two, he'd stomp from that point on, especially with the right enemy/altar combinations. However, the current beta Vampire feels a bit too gimped. Compared to the alpha vampire, which got around by the combination of it's high base damage and first strike on earlier levels, not to mention the simple fireball spamming on mid-levels. The current vampire on the beta can't do much at all on earlier levels. He has no catapult materials and because he can't catapult, he can be seriously gimped early on due to not being able to regenerate properly. I find the vampire often struggling just to beat equal/one level higher enemies, which can lead to a serious xp shortage in the mid-levels. Even if you do beat a single level higher enemy, you're screwed simply because it's not enough to level you up, and leaves you exploring half the dungeon just to get some mana and health back to kill same/lower level enemies.
I dunno, the Vampire just feels too weak. In it's current state, where he can't even worship gods, the exhaustion effect just seems overkill. I've often found myself unable to finish dungeons as highly prepped Vampires, simply because he can't regenerate to take on anything on the early/mid levels. A vampire relies more heavily on luck than (almost?) all other classes in the game - monster locations, glyph location, shop locations etc etc. Playing a vampire on very enclosed levels can be a living nightmare. Maybe I just haven't played the vampire enough yet, but it all boils down to a weak earlygame and borderline insane lategame. A vampire lategame only cares about two things (depending on the boss(es)) - Taking as little damage as possible and getting as much lifesteal as possible (so he's looking to get as much conversion points as possible).