I can't see anyone of the level attainable taking this item; but it would be very very nice for an int-caster twink for the levels where int-casters actually are tanking - that 22 ac will actually come in handy in the teens and 20s for those of you able to pull it off.
Its from Cazic Thule, meaning you can't equip it before level 50 (They didn't change that, did they?). I, too wear a Blackened Crystalline Robe at 53, and still have in excess of 200 int. Saves and hp are walways welcome additions on gear, and the ac is very nice--it may not do much, but every little bit helps.
As an afterthought:
Casters do not tank, but they take hits--debuff too early, nuke a little too much, or trying to get an enchanter pet to engage (there are reasons why you would want to do all these and reasons you wouldn't, its all conditional). No caster can take prolonged hits from 50+mobs, but that doesn't mean they will not take some hits. My 1k unbuffed hp is a joke, so if I have just a 1% better chance that they miss me, or a few points of damage will be shaved off, then I welcome it. I just need to survive long enough that the tanks can get whatever it is off me, or live long enough for the heal to be cast, or get off a spell uninterrupted, or buy the cleric a couple extra seconds to camp out.
well the cha on an AC 22 robe makes this a very nice chanter robe my chanter is 57 and still wears a black crystaline robe and im sure there are others out there with similar robes
now throw in the 4 saves to everything and the 50 mana 50hp and this isnt just a twink robe like you think