I skipped the Void Walkers and Buzzard Wings.

Did the Zeppelin Parts on the druids, since they can loot them in Flight Form.
But skipped them on the other teams I've been leveling for alchemy transmutes.

With 30% less experience needed per level.
And 19% less experience needed from two +exp BoA items per toon.
You can do less then half the quests in each zone, and ding 70th in Netherstorm without touching Shadowmoon Valley.
Or if you do some collections along the way, reach 70th in late Nagrand, or early Blades Edge Mountains.

*Assuming a Hellfire, Zangarmarsh, Terrokar, Nagrand, Blade's Edge, Netherstorm progression.