Another angle of this to consider is rep with factions. I know you're looking for speed, but if you are also looking to get various faction gear at 70 it might make more sense to do instances then quest.

Example: Honor Hold you get rep for area kills in Hellfire through Friendly and mob kills in Ramps and BF through Honored. After all HH rep quests are done it's all Shattered Halls for any further rep. I'd rather have to do 3-4 runs of SH at 70 to get the sweet Blade of the Archmage than have to grind out 12-15, too many flashbacks of helping a guildie grind to revered for the ammo on her hunter.

When I ran my first 70 up I did all quests I could solo then ended up grinding out instances to get what rep I needed (HH rep for the key before the heroic change, earthwarden on CE, etc).
Less efficient use of the rep gains from quests.

My current 2 alts refuse to quest until they have exhausted the rep gains available "cheaply". That means Ramps and BF runs until Honored. Unidentified Plant parts for CE, Arakkoa feathers for LC. The ~13k in rep from quests is much better used to get you into or halfway through Revered rather than partway through Honored. And seeing how easy and fast Ramps is, especially with 4 70 shammies, and the decent pally drops in there, I'd argue for instance until the easy rep is done. BF has a nice spelldam blade for a pally tank too.

(I'm on this because I have a 60 pally and am gathering info and the memory upgrade to box some shammies with him like every other FOTM, but I'm gonna try not to spam the forum and give Otlecs hives)