From your description, I would highly, highly recommend working on another class or three alongside the one you've been working on. The game was designed with that type of play in mind, so if you simply stay with your current class, you're probably going to stay fatigued for the next 30 levels.

Are you playing during off-hours? I'm not sure about Karnak, but on Besaid, there are almost always plenty of people at Horizon.