Not the quality of content. I actually feel they have been releasing some killer DLC lately. The problem I have is charting for most songs seems very subpar compared to RB1-RB3 standards. The last I heard was they were outsourcing DLC, which I wouldn't have a problem with if they would just follow the standards HMX has set from previous games.
Secondly, it has been coming more common for them to use DIY stems. The reason I was happy RB4 was coming back was to get multitrack DLC back. I enjoy customs, but multitrack just adds an extra layer of realism that mp3 customs lack. Even with multitracks, the DLC sounds just like the original MP3 with no modifications to make it better in game.
If I knew HMX would not be able to meet their own previous set standards, I would of just stuck with RB3. I probably should of known something was up when all the faces of the company that we had known "left".