Could we possibly be looking at a hybrid class? Swordsman base class, with ability to split into either DPS or Tank based on soul.

I think that there is one archetype of tank not explored - similar to BLM. Essentially have some abilities move through add stacks of a stance that reduces GCD and applies dots for DPS, and increases parry & evasion for tanks, and some abilities either remove stacks of this or add stacks of a strength buff that increases potency and applies non-damaging debuffs for DPS (vulnerabilities etc) and increases flat damage reduction for tanks, but by a lesser amount than parry & evasion. Tie the effects of cooldowns to it as well. Maybe add an ability that can transfer your stance on a long cooldown.

This would also be in stead of a dedicated tanking stance and in my view is more organic than a straight up stance dance - both stances have defensive and offensive benefits and are more or less comparable but with each stance being optimal for different situations.