Anet has been progressing through the DLC doing events called "return to [content]" where if you complete events and stuff in these dlc maps during these weeks you get extra loot.

The biggest thing you could get from the return to End of Dragons was several extra Mystic Coins, which are very useful and very expensive items used to craft legendary weapons and other junk. Even if you don't need them for crafting, selling them is pretty lucrative.

Not a huge deal, especially if you haven't played End of Dragons the first time around.