The basic lifesteal effect of vampirism now only works on enemies classed as animal or demon. Enemy types were only introduced in 1.0.7, so prior to that it did work on everything. Other enemies seem to be immune (this is supposed to be the case for Blood Magic as well but it seems to be bugged). Note that the lifesteal does actually do extra damage so it's your damage potential, not just your tanking potential, that's hurt when fighting most enemies.
The only reasons I'd take Vampirism now are DotD and Psychic Vampire. DotD is great; it scales with your magic power now, so if you're strong enough you'll be getting 7-8 HP per corpse. Psychic Vampire has a great stun proc (4+ turns, works on anything, might be magic-resistable) and lets you steal mana. If neither of those appeal, take Necro instead and get Pact of Fleeting Life.
My thoughts on the new skills, having not yet tried them all out:
Big Game Hunter: The final two skills have the most potential. It could turn out being used purely as an experience booster, a little like Tinkering sometimes is. Otherwise meh.
Emomancy: A generalist magic skill like Psionics. Looks promising (if not entirely broken).
Werediggle Curse: I'm not sure about this. You'll probably want to pump passive effects/buffs to make it viable, otherwise it'll go the way things like this usually do and end up underpowered as it can't synergise with the rest of your build.
Killer Vegan: Great passives. Not sure if they're really worth the price.
Piracy: If Swashbuckling is anywhere near as good as the description makes it sound, then the skill's worth it just for that level. In fact, it might singlehandedly make melee builds viable in the endgame. Mists of the Corsair and The Black Spot look good too.
Demonologist: Looks decent, and fairly interesting. I'll have to see how Abyssal Fire turns out. If it's area-effect burn, or proc burn, then sold.