I actually get kicked out of DF groups just for boosting?

[Legion88]

It's easy to tell in a few situations, such as a level 60 DRK/MCH/AST with no other Jobs past 50, as you would need a access to Ishgard to unlock those Jobs.

Another is NIN at 60 and no other Jobs past 15 or so since you can't start as Rogue or unlock Rogue until you get access to all ARR City States.

Rogue can be unlocked with level 1 if you start in Limsa. It's a simple side quest near the main aetheryte whoch brings you to their hideout.