I was mostly just curious about the proper order for self-exploration, not so much tours, but your insight is valid. I've just about finished up anyway, with only Ardus, Primus Planet, and the faction-locked sectors (RD, Chavez, Bogeril) left to explore. I'm at EL 28 now, so I'll still need to resort to tours/jobs/missions/whatever for the remaining 20 levels.