They've aleready stated that they will continue adding more sidequests with time. That being said, you don't have to be constantly doing FATEs. What I recommend would be Queuing on the last dungeon you can enter for your level using the job you want to level. Once you've done that, you can craft or gather using another job, you can camp FATEs, you can do levequests, you can complete your hunting log.

This is an MMORPG. The basics of an MMORPG is that it's made to play with others. The team has made it possible to level a job to 50 completely solo, but it is not what an MMORPG is aiming at. The goal is to play with other people. The main way to make exp in a group is by running dungeons. Following dungeons closely are FATEs. Post 35 you will be doing FATE parties more than dungeons because dungeons get harder and finding parties that complete them swiftly without death using the Duty Finder may prove difficult (think Stone Vigil).

You have repetable quests, they'Re called Levequests. they give less exp than normal quests, because they're repeatable. I think it is good, because if they were as good exp-wise, we would see no parties, everyone would just be soloing all the time, and it would be a very boring game. I'm really glad myself that you cannot solo more than 1 class to 50.