Tanking is situational, adaptive and responsive. So is it's gear.

Obviously a fresh tank in low level duties should never be wearing STR accessories. They have neither the mitigation nor utility to deal with it.

A tank facing any target (Boss, Add, Trash) in a group less than 3 should never be wearing VIT accessories. Why? Because AoE DPS is ineffective with fewer than 3 targets and DPS should be using their single target rotations.

On trash pulls, adds, etc (More than 3 targets) VIT gear is advised due to the increased damage the tank will be taking. Allowing more cushion room for the healer to DPS.
Your 100-150 DPS increase will not make up for the 1000+ DPS of a the healer casting AOE.

Obviously STR accessories should not be used in fights where the tank/group is inexperienced. More VIT allows for a greater margin of error on the entire parties part (DPS not dodging, tank busters).