The tabard and achievement system actually encourages you to quest grind to 80 as fast as possible, which you can accomplish roughly 90% solo, then go back and complete the 130+ quests in each zone for the rep and the Loremaster achievement. After quest grinding Borean and Howling Fjord one right after the other (and hitting 75 in the process) I decided it was a better time investment to just hurry up and get to 80, then come back for all the achievements.
I'll skip most of Dragonblight as a result.