Ret 1-40 its the best option, you can quest, heal a dungeon and dps at the same time
at 40 you can go PROT its great for aoe grinding or aoe farming dungeons too wich is faster than questing, or stay ret 1-60 its good for soloing/questing but get good gear pls gear matters
Only go holy if you are running a 5 man for everything and 4 of them are dps, no tanks or respect at 60 to holy