Run an instance and odds are you'll see someone level up. Or multiple people. Multiple times. Instances are giving huge amounts of XP and it's throwing off the leveling curve.
Once upon a time this made sense. It took time to get to instances, to get the quests for them, and groups could possibly wipe, meaning even more lost time. Without XP, instances would have likely been ignored until 60, especially back before they all gave well-itemized blues.
Now we have teleports and the looking for group tool, meaning that instances cost no more time than the run itself. The loot has gotten to be so good that that itself could be enough to bring in players. On my new dwarf shaman I'm finding that instance blues are giving over double the DPS of same-level quest greens. Throw on top of that the change to put quests inside the instances, with their own blue loot and XP, and I think it's worth asking: Do instances need to give XP?
I forgot, thanks to the new city tabards, they give reputation too!
Would you do an instance that gave no XP? Sure you would! You do them all the time at the level cap. Oh but that's when you don't need XP, but leveling is about leveling. Or is it? Players already quest, often running inefficient quests with low xp/hour, rather than the faster and more efficient mob grinding. Not that I'm saying quests are always inferior, after all, if you can get a quest to kill what you're grinding, it makes sense. My point is that we're already leveling in a slower manner in return for quest rewards, story, and variety, so it is that hard to believe that maybe instances could go without XP?