So you do bring certain Tanks for their damage. PLD/WAR for Progression/Learning an encounter. DRK/GNB for damage once you know what will happen.

Therefore long term mitigation doesn't particularly matter which is the problem IMO. Being a Tank should focus on being defensive first and damage output later. Which is clearly not the case.

But that's just a symptom of the dark age of homogenization where everyone is a DPS where the only thing that matters is high damage all the time.

So it ends up just being play the Flavor of the Month Tank.