Ive been duoing with sham/warr while a friend of mine rushed a sham/priest through instances with an 80 warrior.

He went from 10-50 in 7hours played, while I went from 1-23 in the same amount of played. So all in all, RAF XP while powerleveling through instances is amazing, and if done at a decent pace you can get to 60 in a single(extended) playing session.

He did:
10-18 VC
18-26 Stock
26-38 SM
38-45 ZF
45-54 BRD
54-60 Scholo

Believe thats what he did, he flew by me in levels