60 to 80 is all about maximizing your rested XP. If you only have one team then you're going to mix instance leveling and questing. A level 80 will not only help you powerlevel in instance but also speed up your questing. Focus on group and instance quests since that gives more XP than regular quests. With regards to powerleveling at 60, I tried every instance that is possible and nothing comes close to Underbogs in terms of XP/hr. Just clear the mobs until the first boss. 5 instance limit per hour so your goal is to finish it in 12 minutes. The first boss drops Totem of the Thunderhead good for shaman and if you have mining, there is always an adamantine almost every reset. At 66 I tried UK, Nexus and Black Morass and it wasn't as fast as I expected so I went back in Underbogs and will try Karazhan at 68-70.

68-80 is either Outland heroics or Northrend dailies