hmpf well im in the same situation as OP (cept im 29war/mnk lol) just a quick question before i unlock paladin...
WHY DOESNT VIT AND HP MATER?!?!?!
or do you mean endgame o.o
Short easy answer
VIT doesn't matter because you'd have to wear an assload of VIT and still not take less damage over time than using a proper Shield Skill and - Physical Damage Taken setup. (This is assuming something well over your level)
Blame SE for messed up DEF/VIT formulas, the only thing I tank with a lot of DEF/VIT is Jailer Of Prudence, simply because you can reach a high enough level of DEF on him to make him hit very lightly, and he strips shadows so much that /NIN is pointless.
HP matters to a point, but most of our best gear has HP in addition to more favorable stats. Add in that most hard things are tanked /NIN, and you have even less reason to stack on HP when most attacks are being blinked away.
Short easy answer, if someone wants to get technical, be my guest, it's late.