To me the big advantage comes from versatility, you level one class and you can fulfill 2 roles. I also like that it gives weight to the Bonus Point allocation system in the first place, there doesn't seem to be much point if everyone does it the exact same way. This way it forces you to make a decision, not like you couldn't change it later if you wanted to. To me the purpose of the class isn't to use it independent of Jobs but to serve as the foundation to how you approach a given role. That's why I was really hoping to see more classes get a 2nd Job attached since in most every case, the class is indeed useless.