Quests are there for story. Dungeons are for leveling. There is zero reason to use quests for leveling unless you don't want to party at all.

Go do the dungeons, the roulettes, the beast tribe quests or PvP. Those are the things that offer experience. You will never come even close to the amount of experience in X time from side quests as you would from doing these things. This is made that way ON PURPOSE, so that people do not feel forced to do side-quests...and simply because there are so many jobs to level that making quests the way to level would simply kill the game. And as such, quests are NOT for leveling. If you level by doing quests...you choose the single worst possible option (other than just grinding on world maps mobs without any quest at all, that is).

Using the above, you can get multiple levels in few hours of gameplay at any point in the game. Using quests, you will be hard-pressed to get ONE level in an entire day. So yeah...