ARR class progression

[Felis]

It's interesting to see how leveling multiple classes is going to work in 2.0 seeing as how the game is transitioning from a mob-grind based progression system to a quest-based system. For example, you go through an entire series of quests to level one job from 1-50, then switch to another class, are all quests that have already been completed from your first play through gone for good or do you think they'll be repeatable?

They are not repeatable. Simple solution, don't do all quests with only one class ^^
SE bring new sidequests with every big update. And there are still other contents which give exp.