What about creating an ACTUAL Dark Knight?

[Reynhart]

that is a rule you created, and isnt actually a requirement.

It's as much a requirement as having a tank in the party, which may not be necessary if you can indeed burn the content faster than you die. Fun fact, I did FF I, III, VI and VII as an "Attack only" challenge, meaning you only can do normal attack over and over in combat (Limit Break are allowed for VII since they "remove" your attack command). And yes, in those games, it works, so you can skip having a "tank". It's still the primary role of a tank.

im a bit confused here, maybe im miss-remembering FF4, but thought cover only worked when they were at critical hp, and not at full HP.

I've double checked and even in Final Fantasy "II", Cecil had a Cover command. The critical part is a passive trait. In FF III, the Knight has only the passive Cover for critical HP.

but on a side note, im not suggesting PLD cecil isnt a tank, so much as the way SE designed the game, all melee were capable tanks by the standards SE set up, but not necessarily by the standards MMOs eventually set up.

Except that again, other frontline characters weren't able to do any "tanking", and DRK Cecil had comparatively low stats, making this job clearly not a "high def, high HP" job...on top of slowly killing himself. But again, I don't say that this concept couldn't be used for a tank, just that, before XIV, no DRK had actually real tank attributes/mechanics compared to other jobs from the same game.

Most MMOs copied those features, so even in games like FFXI, where they wanted all melee to take turns tanking

They didn't. FFXI was very restricting in the tank department when it launched. Only a PLD/WAR could tank properly since PLD was the only one that could survive at high level, and WAR was mandatory for Provoke. in Zilart, they tried to make SAM the next tank but they didn't realized how broken they made Utsusemi, so NIN took the role. Only years later, you ended with almost all melee that could tank, because 1) Damage enmity was absurd and 2) healers were overpowered. Fun fact, when they crippled enmity from damage, it almost killed every tank except PLD/WAR. (Yet again, it might have changed since, it's been years since I didn't play XI)

[MaraD_]

They didn't. FFXI was very restricting in the tank department when it launched. Only a PLD/WAR could tank properly since PLD was the only one that could survive at high level, and WAR was mandatory for Provoke. in Zilart, they tried to make SAM the next tank but they didn't realized how broken they made Utsusemi, so NIN took the role. Only years later, you ended with almost all melee that could tank, because 1) Damage enmity was absurd and 2) healers were overpowered. Fun fact, when they crippled enmity from damage, it almost killed every tank except PLD/WAR. (Yet again, it might have changed since, it's been years since I didn't play XI)

It wasnt restricted, the problem was they restructured threat, due to how the japanese players were abusing the system before the game came to the west.
The original plan was mobs would bounce around between melee, since cures generated 0 threat originally. (so only melee could generate threat, with BLM not generating much at the time.) Melee lost threat every time they were hit, so any melee being hit for too much, would cause the mob to switch to the next highest dmging DPS.
Magical WSs were very strong, and Banish was extremely powerful as well.
groups went full WHM PTs, and this led to the complete ruin of magical WSs (which have been jokes for years) massive threat increase on cures (PLD was considered rather useless, since unlike the other melee, couldnt generate any threat, wasting all that defense) and i believe most debuffs and spells gained significant threat.
Provoke before this change was more of an emergency CD, since its a seperate pool of threat that decayed way faster, it was meant as temporary relief, in case things didnt go well between the melee. It wasnt meant to be the sole means of controlling all threat always.

THAT is when the game became too much like a typical MMO, and PLDs were the desired tank.
WARs tanking with provoke became a desire, only because cure bombing peopel generated too much threat, and WHMs massive jump into being weaker required tanks to save them. (along with people deciding to fight IT mobs rather than chain T mobs (which were better exp/hour than IT mobs if chained right)

NIN was mostly meant for the utsu to slap onto melee as a SJ, and bounce mobs around again. NINs being able to tank was again, like edge, meant to make them be able to take hits as a melee.
(Which THF struggled with, w/o dedicating too much evasion to, lowering dmg too much.)
The only way THF could have generated threat back then, was after all the melee got hit, and lost threat from the damage they took, putting THF last in line of the melee.
The JP players did use /NIN to do just this, but NIN was so over tuned, it was able to do it solo originally.
Eventually it was lowered to the point of being "good enough", but the idea of having to bounce a mob between them was still similar enough to what SE was originally planning melee to do. (to mimic old school FFs)

But unlike other MMOs, instead of overly balancing jobs, they let the players create the play styles, rather than forcing them. The only time they change stuff, was to nerf exploits, or ways in which players gained more than the devs intended. (like the penta nerf, due to MNKs using high delay 1 dmg weapons for infinite TP.)

When the game came to the US, a lot of the NA players were behind on what was the normal for the JP players, and had a VERY different culture/play style.
A lot of overlap eventually happened once players of both sides intermixed, and took good ideas from eachother of course.