Why in the world would I want to repeat the same old boring fetch and kill quests I just finished with one class with another? Or repeat the storyline quest on another job? That's just silly.

You have plenty of options for leveling secondary jobs. Hunting log, FATEs, Levequests, Guildhests (first time), and Dungeons. In fact, FATEs/Dungeons/Levequests are actually FASTER than quest leveling. I wish I had just skipped all the sidequests as I leveled and just did those, but it was a learning process.