Sorry if this has been asked before, but I did several searches and couldn't find anything about it.
Pre-Cata, it was obviously best to get your butt to Outland the second you turned 58. The XP was way better and so were the quest rewards. However, now that the old world has been redesigned, I thought I had heard somewhere that it's best to keep questing til like lvl 63 or something in the older zones such as the Blasted Lands and Silithus. Is that right? I'm lvl 58 now and heading to Silithus... is that a waste of my time? Should I just go on to Hellfire like always?
EDIT: Also, after Outland... Am I losing XP to go straight to Northrend at 68 or should I stay there til 70? Same with NR.. losing XP to go to Vashj'ir or Mt Hyjal at 78 or stay there til 80 then head out?