Tenacity of Defender - Potency of Attacker = Chance to resist negative effect, with the caveat that this chance can never drop below 15%.
For raids, it can sometimes be helpful to put a character in who can land Tenacity Down, which will reduce the enemy to the 15% base chance of resist even if you have 0 potency.
See AlsoSTAPCool, thanks! That is exactly what I was wondering about.
I'm still unclear about one thing though: Do all debuffs rely on Potency? Like, if an ability says 80% chance to stun, does that mean there is exactly an 80% chance the enemy will get stunned, or there is an 80% chance to attempt to inflict stun and then an (tenacity - potency)% chance for the enemy to actually be stunned?
It's the later. 80% dice roll to even make the attempt. Then it does the potency/tenacity check to see what the next dice roll will be to see if the attempt sticks.
