Dancer Tank!!!

[Februs]

I shouldn't have to remind you we're talking about video games so if you've seen or heard it described as dancing in an anime or movie, guess what? A video game is within poking distance of the same concept

That's true... however, we are speaking specifically about an MMO which has a set and required lore behind each and every job, as well as a Tanking Meta that each specific Tank needs to be at least capable of upholding.
In movies and Cartoons, they can use flashy choreography to allow the viewer to suspend your disbelief for the few seconds you are viewing the bull crap. It doesn't make sense, and they don't have to make it make sense for it to be visually entertaining. An MMO does not have that luxury. The screen is literally a cluster bomb of bright lights, text, and numbers. There is no way to make the Dancer appear to be suspending anyone's disbelief except putting up the words (Parry) over and over again. Now, does that mean they couldn't invent a convincing lore for it? Of course not. You're not wrong to say that the forms of media are within poking distance of one another, and it wouldn't be shocking for a game developer to fall back on silly whimsical nonsense, but that wouldn't make it look any more convincing. In practice, we'd have an idiot doing a tap dance in front of the boss and getting the living hell beaten out of them, and we'd be expected to believe that they were somehow not dying.

More importantly there are certain aspects of the current tank meta that would be absurd to try and apply to Dancer tank. For one, with the exception of rare job specific sets, most Tanks share gear.... so, we're expecting someone who is light on their feet and elegant in their movements to be dancing around in clunky plate armour... really? Not only would this be visually ridiculous, but it wouldn't make sense with the skillset that a Dancer would likely need to employ to hold aggro, because all current and past tank gear are spec'd for physical hit and soak mechanics. That won't, and can't, change. They'd have to completely rebuild the armour database from lvl 1 up to 60. Not to mention the actual mechanics of the boss fights. Tanks are made to soak and recover, not avoid.

I just think tank would work best for the pure dance theme since it could be about dancing out of harms way or distracting foes with your movements. Every other concept likely has some pseudo-magic effect for it to rely on.

This is, actually, exactly the point. The tank meta works in such a way that you don't want your tank dancing out of harms way. You actually want them in harms way so that the rest of the party is not (specifically, imagine shared soak mechanics like in T11 or similar fights. Dancer would be so out of place they would never be used). Which is exactly why all of the current tank jobs are made to buff and soak, not avoid. Even a Dark Knight's Dark Dance ability works with this concept of soaking dmg. It's a mitigation that relies on deflection, true enough, but deflection implies impact. You only deflect a %. Hence, Dark Knights wear armour to protect their bodies.

I'm not saying it wouldn't work, and SE will probably figure out a way just to prove me wrong. I can picture Dancer using mechanics that create stacking buffs to increase dmg/enmity potency for each successful parry or some silly nonsense like that, but SE would have to change a ridiculous number of things in the current tanking meta to get this concept to work out (Fixing Parry so it wasn't a tip toe shy of being useless would be the first among them). Personally, I think it's just too much trouble to try and make a job work with a meta that wasn't designed for it.