You really had to scramble for examples there. Ones that leave me quite confused as to your central point, actually.
I actually replayed all 3 games not long ago.

But the kicker is, the demands of a single-player turn-based strategy game are different from those of a real-time MMO.
Turn-based strategy games don't have to follow the Holy Trinity. You can have debuffers, suicide bombers, turn manipulators, jacks-of-all-trades, all sorts of jobs that would be overpowered/underpowered/impossible to translate into competitive jobs in an MMO, and jobs that would be frustrating to play alongside in a cooperative manner if the whole party isn't being controlled by the same person.
Bravely's Dark Knight is a job that sits on low health for as long as possible so it can deal damage -- not exactly the pinnacle of reliable tanking, solid example of a DPS that drops from relatively durable to glass cannon though. Based on its optimal setup for maximum stats, if a non-spellcaster looks in its direction, they could sneeze too hard and kill it. Now luckily, its stat boosts are snapshotted based on damage taken and last for multiple turns, so it doesn't have to stay at low HP -- but it needs supplemental HP for the defensive buffs it receives to actually matter. And to replenish them once they run out.
That's not really fair is it?

But also, I never once argued against a tanking job having mitigation.
No, you said DRK was never meant to be a tank in past FFs. Yet it had a ton of mitigation tools and boons from getting hit, which is also a tank trait. Calling out its sustainability in a single player game is just bad faith. I mean, the Bravely DRK even has Living Dead basically.

The point was, use past FF DRKs to form a tank identity in 14 and a DRK that's unique to 14.