I leveled all the way from 60 to 85 in the Eastern Kingdoms on a prot pally. Got the Destroyer of Worlds one evening and switched to ret; I like the looks of it. I had zero problems - the XP scales with your level. He works in Northrend now, collecting Vyr'Kul artifacts. It's marginally slower, only because you're no longer scaring the various mobs to death with a single glance.