I found this guide on another site, I had a flick through some threads and couldn't find it, so I thought you guys might want to take a look!
Cred's to Stivenator.
THIS IS WHAT HE SAYS...
"Okay, so my friend told me about this exploit and at start I didn't believe him.
But then we tried it and I got him from 84-85 in about 30-40 mins when he was rested.
So here's a video. Notice that this only works for horde!
"