Yoshi-P New Classes/Jobs Release Plan.

[sharazisspecial]

The Dark Knight as a draintank could be interesting, But the amount healed would often go to Overheal anyways, much like our existing Warriors.
Dancers wouldn't make sense in a Tank role. You wouldn't be wearing heavy armor, and you'd be relying purely on RNG to avoid getting creamed in one shot by saaaay Mountain Buster. The same issue the WAR currently has on Titan, no effective way to reduce that massive shot.
The concept of a Magetank sounds fun on paper, but I've never seen one, in any MMO, that pulls it off properly and i don't think XIV will be the one to manage that lol.

Look at wow brewmaster monk's tank or just their tank mechanics in general

WoW monk tank has trait(stagger) that causes 20% damage taken to happen over 10 seconds.
They have a ranged aoe taunt that doesn't require a target .

WoW Tanks have quite a variety in abilties to make them unique. FFXIV new classes can be unique too.

Our current tanks have RNG mechanics too. Block and parry.