We recently made a change to the way experience is calculated and wanted to take some time to explain this change in order to clear up some confusion some may be having in regard to their rate of progress. If you are currently at the maximum level that you can be for an expansion (or higher), killing creatures from that expansion will now grant 10% of normal experience.
Level 60 or higher players get 10% normal experience for killing creatures in Azeroth (“Old world” content)
Level 70 or higher players get 10% of normal experience for killing Burning Crusade creatures.
Level 80 or higher players get 10% of normal experience for killing Lich King creatures.
Level 85 or higher players get 10% of normal experience for killing Cataclysm creatures.
What does this mean for those that have Cataclysm and are leveling up new characters? This means that you will gain normal experience through to level 60 and will then need to move on to The Burning Crusade zones until you reach level 70 and Wrath of the Lich King zones until you reach level 80. Once you reach 80, it is expected that you will be continuing your leveling adventures in the new Cataclysm zones and dungeons. We have made this change so that players will continue to progress through the appropriate content for their level versus grinding on quick re spawns in a less ideal location.
This change will also affect hunter pets and their leveling rate if the player is at max level, however, this is an unintended change that we will be addressing in the future.
The content for The Burning Crusade opens up at level 58 and the content for Wrath of the Lich King, at 68. It's generally expected that you'll want to move into those areas sooner rather than later and finish leveling to 60 or 70 (respectively) there. We fully understand the feeling that you're being moved out of the new cool stuff, but at the same time, the leveling rate for Burning Crusade was already elevated with the release of Wrath of the Lich King and the rate for Wrath of the Lich King was also recently elevated, which should help you move through those areas relatively quickly.
We also have remarked that if we are able to at some point in time, we'd like to revisit Outland to make it a better experience to move into.