Love Paladins and Warriors but there is no contest between them and Mages when it comes to speed boosting. I suspect that even pet boosting with 3+pets would not get anywhere near this fast as it would slow down as you got closer to cap.

This time with essentially no rested XP a Mage boosted a single character from 1-60 in 1 day 16 hours and 20 minutes in game time (40.33 hours played) over an elapsed time of 2 days 2 hours and 38 minutes (50.63 hours total time). I think the ~10 hours between played and total time was the time he took to nap/rest and otherwise do admin/prep on his other account.

This was done by mainly a level 60 Mage boosting a Mage from 1-60 with both Mages mainly doing large pulls by leveraging pathing with blizzard (sometimes only the 60 AoEed, only the leveling character AoEed, or they both AoEed). As far as I saw (I only reviewed some of the footage) one person played both Mages and otherwise they had a 2nd person on his Warlock doing resets of instances and going ahead and summoning them to the next locations once they out-leveled a given area.

I didn't review all the details but there were some definite banking of mats for turn-ins for XP which shaved off at least a few levels but then again it was on a PVP server and he was stream sniped for at least 4 hours (possibly more). There may have been some open world mob tagging (not sure) but most of what I saw was instance based pulls...

I suspect there will be a summary video put to youtube at some point but for now the raw footage is here:

https://www.twitch.tv/arlaeus/videos