Like Jeeq said, overworld was populated because we were out there doing FATEs. This is because we had a hard stop at (I believe, it's been a bit) level 47 where we ran out of MSQ experience and had to go do FATE farms to get the next quest.

Having to level two classes was also pretty annoying, because they often were two different styles of play. So you're jiving with this class that you love but then you get stuck not able to progress to the Job step because you have to stop at 30 and go level this other class to 15 before you can keep jiving with the class you were enjoying.