The 4th Tank.

[Cooperal]

If it's another simple plate-wearing hit soaker, I think I'd start keeping hold of my sub money. Three is enough, if not too many. You can throw as many mechanics as you like at the next job that simply stands in the way, they aren't going to succeed in feeling different.

I'd like something like Dancer to be the next tank. Something that literally requires quick foot-work on the part of the player, not limited only to some fancy flips simulated by the press of a hotkey.

What they miss in defence, they make up for with evasion and a larger than average array of tricks to waste an enemies time. With the help of their own decoys, stuns, petrifies etc, they will be able to move around, use positionals that are unconventional for a tank, and then be back in front in time for the enemy to regain mobility.
Without a doubt, sequencing and timing will be a part of the dancers playstyle too. They should have a 1>2>3 GCD combo, defensive/enmity based ones, but on the condition that they sneak one of a choice of oGCD abilities between each GCD in that combo. Like a load of mini-dark arts.
Of course, some bosses hit hard as hell and it would not be viable to "trick" your way out of them. That's why they should have at least one equivalent to Shelltron (or FFXI ninja shadows) in reserve. Other ideas would be like the DRKs plunge but it puts you on the opposite side of the enemy (sort of syncs with the positional idea).

Their weapons of choice? A pair of fans of course! Give them an oriental vibe to slot comfortably into Doman lore.

Skill speed and accuracy may be key stats to them. While dexterity may function like a highly enhanced version of strengths damage mitigation (this would also make it easier to fit them into gear that already intended for Nin, Brd and Mch).