I feel bad for people that leveled a DD for their first job. Having to wait forever to do a dungeon kind of sucks. And it's even worse that you have to wait to do a dungeon to progress in the main story.

So if you're a DD, you're at the mercy of the duty finder to progress.
Or you could make some friends I guess lol. But still, it would be annoying.

Best way to level is to level a tank or healer to 50 so you get the bonus to FATE exp for your next jobs.