I've made my thoughts on vampirism before, and everyone seemed to be torn between beating me up over it, and agreeing that it needs some change. Honestly, vampires not having massive health regeneration goes against Vampire lore anyway, but this game isn't meant to be fully in tune with Vampire lore. They may not regenerate lost arms in 20 seconds or something silly, but you pretty much can't stop them for too many days by cutting off their arms and legs. Also, because it was mentioned several pages before, "Die, monster, you don't belong in this world." "It was not by my hand, that I was once again given flesh! I was brought here by humans who wish to pay me tribute!" "Tribute? You steal men's souls and make them your slave." "Perhaps the same could be said of all religions." "Your words are as hollow as your soul. Mankind ill needs such a savior as you." "What is a man?!? A miserable pile of secrets, but enough talk, have at you!"
I'm proselytizing again, but I have to say it one more time: Vampire/Vegan/Magical Law + whatever badass melee build you like. It's trivial to gain one level off of non-animal monsters, and once you have Polymorphic Injunction, it's easy to get all the XP a dungeon level has to offer. Personally, I went Injunction --> Level 5 Vegan --> Drinker of the Dead, because once you have the +6 from having all 5 levels of Vegan, Drinker of the Dead is enough to keep you at 90%+ health full-time, even if you never vampire-drain an Animal in your entire run. I highly encourage Communism simply because +5 from Iron Curtain goes a long way for a naturally-defensive Vampire build (and another +1 each from Socialized Medicine and Vanguard Party aren't bad, either), and some way to get mass resistances (Warlockery? My character ended up with Rubber Pants and a host of other resistance-building items.) If you want to tack on Smithing, you can almost certainly craft a couple of those emerald rings that give out by the third or fourth floor, too. Vampires are totally legit in GRPD, and they don't have to be Master of Arms/Shield Bearer, either. There's also a few badass variations of Vampire/Necronomiconomics (vampire provides , and Pact of Fleeting Life doubles your healing power). Once the weapon revamps go live (assuming they're not bent over a barrel and spanked like a stick of butter), Vampire/Unarmed will be pretty fly what with Bully Stance granting +2 right out of the gate and Unarmed in general giving a massive +4 HP/level. And then of course there's the synergy between Vampirism and... Tourism: +1 at the start is nice, but the real strengths here are Meet Interesting People (cannon fodder for your feeding) and Sample the Local Cuisine (eat even though you're a vampire!). Promethean: This is a little obscure, but Wyrmling is the only spammable Animal pet, making Promethean the best bet for a vampire nuker wizard -- the MP->HP efficiency is incredible as long as you have several turns to rip into the tender flesh of your newly-summoned pet. Fleshsmithing: Zombys are clearly not as good as Wyrmlings for shredding, but they're cheaper, come in greater numbers, and still give 2HP per attack. And if you get Meatshield running, the +4 is very nice. Knit Tissue, of course, is even godder for a Vampire than it is for someone who heals naturally. In short, Vampirism's problem has nothing at all to do with it's fundamental nature -- there are LOTS of good ways to build around that. Vampirism's problem starts with the fact that Sparkly Glamour sucks balls...and really, that's about it. Psychic Vampire's mana might not matter to a straight warrior, but the confusion proc is still solid, and Transylvation is solid no matter who you are.
Yep, after all Wootah changed that one, not the entire idea of the tree, it just tweaked a little with scaling... but your idea could work too, I'll try the new ESCR to test this.