Don't worry about which is your "main" until you've worked on playing one of each to max level, since you plan on doing that anyway. If you want to make your first leveled job a tank for faster queues that makes perfect sense, but you might find that you enjoy one role more during the leveling process or at max level, and the only way you'll find out is by playing. Nothing ever locks you into one job until endgame gearing, and even that can be easily reversed every major patch.