I have not seen anything confirming a real tenacity/potency formula, but that multiplicative model by RFC (above) doesn't really work.
For Example, Sidious has 0% potency, the rancor has SOME sort of tenacity (assume for this example, 50%), yet every once in a while sidious is allowed to land a dot or heal block. Using a multiplicative model, sidious would never land any negative effect.
It is seems more likely that there are separate formulas for an effect triggering vs and effect 'taking hold'. So for sidious landing a heal block, the first calculation is:
- 1st check if heal block 'activates': chance to activate: 100% chance to trigger
- 2nd check to see if tenacity blocks it (if it triggered): 50% block chance
- 3rd check to see if potency can overcome the block (if block occurred): 0% chance.
That model doesn't quite work either though, because Dooku has ridiculous potency, and you've probably seen his stun get resisted plenty of times. So it's much more likely that there are 2 checks involved, maybe something like:
- 1st check to see if heal block activates: 100% chance to trigger
- 2nd check to see if effect takes hold: (tenacity / 1+potency) in our example, the resist will be 50% / 1 = 50% still. So a 0% potency sidious still has a chance of landing a heal block!
