I went to nothrend (solo DK) at 68. I skipped Blades Edge, Terrokar, SMV, NS totally. I hit 70 before getting the "nothing boring about borean" acheivement. If i play it right, I'll finish borean and hit HF, doing everything I can until i can get acheivements on every zone should put me at 80 in zul'drak. RL friend of mine started in Borean at 70, then HF, Dragonblight, Grizzly Hills, and just went to zul'drak last night, he's 5 bars from 79. The idea of Scholozar, Storm Peaks, Icecrown all being gold is pretty awesome.