Also worth noting: in ARR you can complete most MSQ and sidequests as a DoH/DoL (so long as you're at the correct level for the quest) and receive the reward EXP into that class. You don't need to have it equipped the whole time, just for the final step of talking to the person with the green "complete quest" marker.

They 'fixed' this in Heavensward, but it still works for ARR content.