I would not recommend you go pure vitality as if you are serious about going tank you will only be able to play catacombs anyways. There will be a healer to help you recover your life, adding points in vitality then only serve the purpose of giving you +defense on your armors, which IMO is negligent compared to the bonuses you could be getting otherwise, from other aspects of your gear.
What we need to understand is that monsters will be dealing you 3 types of attacks, these are which your looking to reduce.
Magicial attacks
Physical attacks
Critical Strikes (ignores defense)
If you want the best possible tank armor I would recommend you use a very high EE scale armor. Were talking 180+ EE here. The reasons for this are that a plate/chain mail will give you less of a damage reduction from magical attacks and a high EE scale can achieve the same plateau effect as a chain/plate (at around 140EE a plate mail works as well as a 220EE plate since your already reducing all physical attacks to 0, chain 160 EE, scale 180EE (approximately)).
Now that this is done you'll need to concentrate the rest of your stat points on a balance between dexterity and intelligence. Heres what I would recommend. Try to hit 80-100 dexterity and then put all your remaining possible stats into intelligence. Intelligence will help against the magical attacks as well as giving you the possibility to use a heal charm, making you not completely useless in catacombs.
The reason were putting more importance towards physical defense is that I have reasons to believe the ratio of physical-magical attacks would happen at a 66(60)% - 33(40)% ratio.
Of course your remaining gear choices could be Healmastery or w/e to help you heal better or you could focus on +int, +dex items for more tanking ability.
tl:dr, the best possible realistic tank would be like this imo
str- base
dex- 80(100)
vitality- base
intelligence- 70+
armor- 180+ EE scale
weapon - preferential
charm - preferential
acc.charm - EE heal charm
edit:
Oh ya, make a fighter not a barb, heck even a rogue could be better option then a barb in 1.18 IMO
This post was edited by arxyn on Dec 19 2009 10:06pm