Blackrock Depths - 70
Lower Blackrock Spire - 70
Dire Maul:East - 70
Dire Maul:West - 70
Dire Maul:North - 70
Scholomance - 70
Stratholme: Live - 70
Stratholme: Dead - 70



As you can see, 70 is the way to go. All the old world instances are not viable for xp anymore. Questing is the way to go.