If you're trying to level two jobs, keep the levels slightly unbalanced so one gets the armoury bonus (+50% EXP).

You might be better to "run to the finish" with one job through MSQ at this point while using the other for daily roulettes and sidequests, or you're probably going to have the same issue again at the future sticking points.

From memory you don't even get enough quest EXP to get one job from 78 to 79 without having to do a dungeon or two, unless you're already ahead a bit.