How do tank mitigations stack?

[aodhan_ofinnegain]

Stacking shouldn't really be a thought, aside from something like Rampart and Arm's Length or reprisal and your 25 sec CD. You want to spread them out as much as possible, depending on the DPS output you're dealing with.

In dungeons yes, you space out your mitigation, certain tank busters in Savage and ultimate however, you do need to stack, it was especially the case for e12s door boss which hit exceptionally hard, you had to stack multiple mitigation cooldowns or invuln.