Tank IDENTITY

[Seku]

People once made the argument at one point that 'defensive tanking' and parry builds could be used to optimize healer dps as well, back in ARR. It generally doesn't work out that way in practice, and there's no clear cut way to determine a dps equivalence for it.

Assuming you're talking to me, that's a different situation, or at least their use is. The people that made that argument probably will still argue that tenacity is a very good stat despite providing almost no actual value in most things. 'Defensive tanking' and 'parry builds' should be going more towards passive damage, which hasn't been a threat in this game for the most part. And you're right in that you can't calculate that damage too easily because it's unexpected in most cases. But it also serves an entirely different style of combat that would only serve a purpose in something like deep dungeons.

On the other hand, using mitigation purposely and with thought for something you know is coming can indeed be translated to a rough estimate of DPS gain and loss or at the very least potency gain or loss. The most simple example without going into too great of details would be that a PLD uses invincible to take a tank buster. Assuming the healer doesn't have any oGCD's up this would be a net gain in DPS as it doesn't take the PLD's action (GCD) and it doesn't take the healer's action ( GCD), thus allowing for the healer to continue their DPS.