I bought WoD and tried to play WOW again for a bit and you are really punished during leveling. I like to complete a zone in it's entirety. You can't do that in WOW. If you do the amount of XP that you earn in the zone is reduced so much that it's almost pointless. In my case it dropped from over 10k XP per quest to something like 100 XP or 200 XP. You don't really get a chance to experience the content because the game forces you to skip half of it. You can't use an alt to complete the zone because part of the quests are chained and you would have to redo other quests.