I'm in Act III currently. At first I didn't equip any vitality gear whatsoever - until I died somewhere in the middle of Act II. Gradually, I added more and more vitality into the mix, until I felt comfortable again. How large a HP pool do you shoot for? Depending on Act and difficulty setting and class?
Demon Hunter (normal)
- Act I - 500-1000 HP (somewhere between none and some VIT gear)
- Act II - 1500-2500 HP (definitely be on the high end of the spectrum farther into the Act)
- Act III - 3000-???? (just began here, started out with 3k HP and already pushed it to 3,5k with VIT/DEX gear from the AH)
My itemization tip in general. Everytime the blacksmith has a new class and level appropriate item to build, go check the AH for a suitable piece, rather than building one yourself. It'll come cheaper.