I was 2-boxing with my Warrior and Paladin just using research of quests using Thottbot and Allakhazam. The way I approach it was search Allakhazam for Prot Gear my paladin was gearing for. My warrior was just there to add dps on top of the Prot Pally survivability.

It took me 2 weeks from 60 to 70.

A friend who ran a hunter had the paid guide but also levelled around 2 weeks.

The main difference between me and him, I took the research and wrote my notes with where to go (locations).

My friend said he had to look up quest links sometime to find what he needs to do next based on the guide being somewhat not having the info he needed. But my friend was a solo hunter, and I was 2-boxing melees.