As people have said run the highest lv dungeon you can run. Complete the challenge log that pertains to battle class xp. Beast tribes, eat food, side quests if you haven't burnt them all on your main. Heck even though I avoid it like the plague MSQ roulette gives a decent chunk. Also front lines as you can que up on the job you want xp on and switch to your main or any other job you enjoy doing pvp on. Hunt log for any class/job that's from ARR up to level 50 and your company hunt log.