Guild Wars 2 dynamic levelling system adjustment "allow players to enjoy content on any map at any level."

Isaiah Cartwright, lead game designer, posted on the blog about the change. “We had a few issues with this system that we made adjustments to. When high-level characters played in lower level zones, they were a bit too powerful, so the content was not as challenging as it could be. As a result of this, we also scaled down the rewards a bit too much.”
As of January 28th, the new build introduced two key changes:  
1.) The formula for how attributes are calculated when the dynamic leveling adjustment system scales you down. This makes returning to lower level zones more fun and better balanced.
2.) The formula for how rewards are calculated when scaled down to make it more rewarding for high-level players to visit lower level areas.
Although this will mean that areas are harder, they should also make them more fun and challenging. This can then justify increasing the loot available to higher level players, as they have more of a chance to find loot for their actual level.
Isaiah ends the post on ArenaNet’s plans for this year, “In 2013, one of our main goals is to add more content to maps of all levels, as well as stronger reward structures for playing across all locations in the world. This will give us a strong structure of experiences, challenges, and rewards that are balanced for a player of any level in any map and help make the social experience of playing anywhere in our game more exciting.”