The thing is we are assuming each class had a definitive party role. Each class has the ability to do certain things more effectively than others, but for the most part all the classes can do anything in this game.

Ranking GLA to 50 to tank is not a complete goal. Classes are just different proficiency sets with weapons and tools in this game.

This is why the dev team is introducing Jobs. Jobs are essentially roles for a party - enhancing the party gameplay.

Until we get Jobs to give us bonus skills that maximize our proficiency in them, it is up to us to gain experience with a variety of weapons and tools in order to more effectively tank, DD, heal.

It's an assumption to say that ranking GLA makes you an effective tank, or that ranking LNC makes you an effective DD.

Classes are not jobs.