Just to throw a loop in this whole thread. I've found it actually faster to level my Pally, 4 Shaman team up. 26-60 in 2 weeks actual time, at my rate that's about 4 day's played time, works out to about 4-6 hours a day (for me this is about 8pm-12am as that's when my kids are sleeping). Some of the milestone levels like 30,40,50,60 i spent more time that day, but i got about 2-3 levels every night just doing Quests. At 60 my team had 5 day's played. I did not grind any normal mobs, or did i hit an instance for grinding either.

I ground Deadmines, Shadow Fang and RFK getting gear and leveling in the instances, but quickly found that to be way slower then actually going out and doing quests. The biggest problem that i found was not having enough quests worth doing before i was high enough level to get to the next zone.

Level 30-40 was Duskwallow Marsh, Arathi, Hillsbrad, Stranglethorn Vale.

Level 40-50 was Tanris, Hinterlands, Searing Gorge, Burnning Steeps, Feralas, UnGoro Crater Zul'Farrak (2 levels in ZF 1 killing mobs, 1 on quests 44-46)

Level 50-58 Was Eastern/Western Plaguelands, Wintersprings, Silithus, Felwood, Black Rock Depths (3 levels just in BRD doing quests and Ony Attunement)

Level 58-60 Was Hellfire Quests which only took about 4 hours to do the whole zone.

Next up for me is Zangramarsh i'll let you know how long it takes me to do that zone.