Pavonis Interactive Forums

When the AI decides who to shoot, does it factor in armor ratings, especially item armor ratings?

This translates to whether it is useful to stack armor and tactical vest mainly on the low-defense tanks or not.

With 99% of cetainty - NO.
They prefer to shoot characters who they have the highest chance to hit, and also guys who are low on health, and, surprisingly, hacked robots and turrets (but maybe that's because they can not have any cover bonuses in the first place, and thus are easier to hit).
That's why the whole tanking tactics works (chars with negative defence but lots of dodge, armour and health).