A quick description of what I's like and why:

Samurai TANK: stacks system that goes up the more hits you take, so you can unleash powerful blows like Bonecrusher. A DPS stance based on drawing your sword where you lose your ability to auto-attack but counters every hit you take with a 100 potency Iai attack.

Red Mage HEALER: only role in this game where you can use both attack and healing magics without people getting mad at you. Mechanics based on doublecasting (instant-cast 2 spells, no MP cost), one melee combo for MP management.

Dancer DPS: Think Monk without the stacks and each "Form" would give the nearby party members a different effect, so, depending on how you want to support them, you rotation would differ.