Note that you do need to do ALL the Main Scenario Quests (or what I called story quests above--oops) so that you can progress to the new content in the Heavensward xpac. It doesn't matter what combat class you do them on--so like Reinha said, if you dislike your class choice you can pick another and level it to the point in the MSQ where you left off and continue on--but you do have to do them all.