There is a precedent in MMOs to add content in patch cycles. For example, we're getting new dungeons and loads of changes in 2.1. This is really bad design.
When 2.1 hits, it's going to be shiny and new for about a week or two. After that, the content will be old-hat and people will start waiting for the next patch. Players consume content faster than it can be created. Unless content is insanely difficult (turn 5) or uses artificial limitations (myth caps), players are going to chew it up fast.
A simple solution is to stop the patch cycles. If you get a dungeon or feature to the point where it's ready to be tested, test it and then release it. Don't wait for the patch. Just get it out the door. This means we're getting new content every few weeks, not every few months. This difference could mean a huge perception change for the game and make it feel fresh more often.