My first set of toons went tot he Outland at L60 and quested their way through to L70 at which point they went on to quest through Northrend. These toons were in the L70 zones when they dinged L70. By L75 they had completed almost all of the quests for their level and were struggling to find quests to get to L76 to enter Sholo... basin.

My Second set of toons, wen to the outland at L60 at which point I point the alterac valley queue,and quested whilst waitiing for AV.These toons were barely ouut of nagrand when they hit L68 and went to northrend. Still joining AV as much as possible, they are now L75 in that Zul zone. they skipped most of dragon blight due to outleveling the zone.
Av boosts questing exp trmendously and is a nice diversion from doing the same quests again.