End Game: AC vs. HP

[Vayder]

Depends on the mob you are tanking honestly. You have to take into account how much of the NPCs damage is coming from DB and how much is coming from DI. If you can use AC to measurably decrease the average DI then it's worth swapping for AC gear within reason. However if your AC isn't going to affect the mob's DI you're much better forgetting AC and taking all the HPs you can get.