A hotfix notice was posted to the forums not long ago warning of an impending change
: level 1 to 60 dungeon quests will award significantly less XP. While few players will be fans of such a change, I do think it's a smart one. In the blue post below, Zarhym says that players were outpacing the questing progression because of these quests, and it is absolutely true. Using the dungeon finder and completing the quests in each dungeon threw off quest and zone progression completely. When my dwarf shaman finished all of the quests in the Wetlands, she already had Hero's Call quests from the board in Ironforge urging her to skip multiple zones ahead. Not what you would call a great leveling curve.
We are applying a hotfix today to all level 1-60 dungeon quests for Kalimdor and Eastern Kingdoms dungeons which will significantly reduce the amount of experience they award.
While dungeons should remain integral to our evolving storylines, and great places to collect gear in cooperative environments, we need to make sure each player's questing progress remains relevant as dungeon quests are completed. In many cases we're seeing players enter dungeons to complete quests, only to come out ahead of the leveling curve for the zones they're in.
This change should allow players the opportunity to reap the benefits of running dungeons, while not outpacing the leveling flow from levels 1-60. At this time there are no plans for making any adjustments to dungeon quest experience for Outland, Northrend, and level 80+ Cataclysm dungeons.
You can find a list of all of the latest hotfixes here: http://us.battle.net/wow/en/blog/1232869