I went to Hellfire at 58, but my plan was to spend a lot of times grinding instances to ensure that I have the faction for the pvp sets. I'm 68 now and have only quested in Zangarmarsh and Hellfire. I'm honored with all the factions for the pvp gear except the helm which requires Sha'tar. Honestly my eyes are about to bleed from doing so many instances and I would recomend questing a decent bit to break up the monotony.

With the RAF bonus I see no reason for jumping into outlands before 60. You should be no where near running out of quests on Azeroth.