Well Enmity for one is almost a non-factor anymore. Every tank gets tank stance at level 10, and every attack under tank stance generates enmity, so its practically impossible to not have aggro, Which means its practically impossible to take aggro with a Non-tank class.
I know this is late since in discord you mentioned how your rolling Black mage ( good choice for dungeons btw, their aoe is amazing. please use aoe lol) If BLM turns out to be not fun you can roll any job you want on the same character. without expansions there is 10 i believe? though i think you have all the expansions so theres 17. 2 when you get to level 50 ( Red mage and Samurai) and 2 at level 60 ( Gunbreaker and Dancer). Unfortunately for Machinist, AStrologian and Dark knight you actually have to get to a certain point in the story but youll get there eventually.
I dunno if any of this alleviate any fears, but goodluckko.