Eh, the paladin isn't levelling but boosting.

It's a decent exploit of an oversight Blizzard made, I guess, but there's much faster things to do with a Prot paladin boosting you. 20-42 SM Cath/Armory (alternating to avoid lockout). 42-45 Uldaman, back door. 45-58 Stratholme trash between the entrance and Live (video
here). Stratholme at least averages 100k XP/hour according to the maker of that video. Unrested. Although that is with a full group (XP is maxed per character with a level 70 in the group; with a group, you get a group XP bonus).
Black Morass is
insane levelling with a passive uncrushable Prot paladin. 10k+ XP/minute. (Yes, you're reading that right.) Of course, you have to be level 66 to get in (and complete Durnholde to boot), but once you're there...