It’s the age old question: Is it better to kill everything in sight with no thought to the pile of yellow exclamation points awaiting your attention, or carefully go from quest to quest, compiling experience and rewards as we go?
Blizzard is known for its grind quests, which send you out to kill sixteen of those and gather five of that. They can be tedious, long, and excruciatingly frustrating - especially when you throw in farmers and low drop rates into the mix.
Looking for group? Not really
On our way to 60, these grind quests were broken up by instance runs such as Uldaman or the Sunken Temple. Instance quests were plentiful, and the experience gained from killing mobs and completing quests were usually equal to if not more then the amount gained from solo grinding outside the instance. But that's just not the case in the Outlands.
There are few quests for the instances of each zone, and while the rare drops and rewards rule, instances are not the way to go if you've got your sights on level seventy. Even when rested, the experience gained in an instance is at best equal to what you could have gained by soloing outside. So other than needing the gear or the reputation instance runs provide, they are not a viable option for fast leveling.