If you like doing X activity level a job from list X. If you like doing Y activity level one from list Y. If you like doing both X and Y level one or more of each or a job from list Z that can participate in both. If you like doing X activity but only enjoy playing a job that is good at Y then you're SOL. Is that pretty much the formula we're going with here?
If we didn't, why have multiple jobs at all? Why not just give everyone everything then everyone will be able to participate all the time in any role they want!.
But then again SE also implemented a wicked awesome system in this game, really unlike any other MMO...we can change jobs depending on what we feel like playing.