The 4th Tank.

[Duelle]

As much as I love BLU, it probably won't make an appearance in FFXIV no thanks to how it is setup to have a set number of abilities and traits on all classes.

Still needs a lot of cleanup, but I just want to prove BLU can be in this game.

I wouldn't mind the 4th tank being based on a similar model to WoW's Brewmaster Monk or Guardian Druid. Evasion based using either a huge health pool to mitigate bad streaks, with self-heals to supplement healers. Or a shunted damage pool that absorbs a percentage of damage taken, which then slowly bleeds the excess damage back to the player. Dancer could work as the latter, Beastmaster as the former.

Personally, I figured SAM would get something akin to the Brewmaster's Stagger mechanic. It just seems like a natural fit since samurai armor (traditionally lamellar stuff) isn't as sturdy as plate and if we were to go by real life analogs, SAM may end up with lower native defense compared to PLD, WAR and DRK. Some adaptation of Shuffle would work for Dancer if you want to make it a tank, though you'd need additional mechanics to make it work.