I have been wondering this myself and while I leveled I put all my points into STR. Hitting 50 I decided I would reset them and add them all to VIT and see how it worked out. Well it works just fine i have no trouble holding hate even without the 30 in STR and from what i have heard your only getting a 1% increase in damage reduction with 30 points.

So I am for the VIT, myself, I have run Amdapor Keep with the points in VIT and still had no trouble holding hate. (I was in a very good group, which always help, and they waited for me to grab hate and cast Flash before attacking, also they watched their own hate to make sure it rarely pulled the mobs away from me). The Extra VIT really did help with a couple close calls that if i did not have it i would have been dead for sure.

More health never hurts and usually will keep you alive longer which is what a tank needs. Now I know others would disagree, however it has proven to me to be the better choice.