For nin, I would change Doton to have the same potency but a shorter duration so that immediately recasting it when mudra cooldown is up doesn't clip the last 1-2 ticks. I'd also make Huton a passive trait you get when you get your third mudra, and change Armor Crush in to something more interesting.

For tanks, remove the damage penalty on tank stance entirely while locking defensive cooldowns behind it and adding more powerful active mitigation tools to it to make you want to be in tank stance more while also making the gameplay much more engaging for the tanking role.

For brd/drg/mch, get rid of straight shot/heavy thrust/hot and fold their damage boosts in to the job or add the buffs to their normal dps rotation in the same way sam's buffs/debuffs naturally fall in to it's Sen generation as a baseline.

For smn, I'd just add a 1-2 minute cooldown that instantly does the remaining damage of their dots on the target instantly while consuming the dots at the same time (little hard to word it, I think you get the basic idea though) so a smn that knows a fight really well can use it before certain jump mechanics and not waste dps uptime.

For blm, I'd turn Enochian in to a passive and remove the timers on astral/umbral. I'd also have Fire 3/Blizzard 3 replace Fire 1/Blizzard 1 respectively while maintaining the same casting time/mana cost as their level 1 variants.