I haven't gotten up to the higher-level camps(but I remember checking around the kobold camps before and they were packed tighter than sardines in a can), but from what I've seen thus far in Limsa, enemy levels usually only have a one-level difference between them, and the only things I've seen link thus far are mobs that aggro anyway.

And once again, the game should have soloable content and for the most part it does, but there should ALWAYS be more incentives to party. You want the big boy XP? grab a group of people and go nuts.