SE encourages players to not only play one single class/job but also play other class/job as well (I'm only referring to the DoW & DoM).
I do agree that leveling your main class/job isn't that hard, but once you start to level your 2nd or 3rd class and so on, then the problem arises. You barely have any quests left, leves aren't that rewarding, and FATE grinding could be a problem if there are not many people at the same levels playing at the same map. Then at that point, there are barely any options, you have to burn the leves allowances or keep FATE grinding (provided there are many people doing them as well).

Well I hope there will be a solution to this, otherwise the idea of leveling other classes is really not appealing.