What's wrong: content is missing, missing from select regions or priced incorrectly. This is bad. Unfortunately, we don't maintain any of these stores ourselves and can't fix anything without help from Sony.
What's being done to fix it: all the issues listed in this thread have been flagged to our support rep at SCEE. They have a limited number of testers so we are somewhat at the mercy of their schedule, and for a game that releases more content every week than most games do in a year, I'm sure you can imagine that we are already keeping Sony pretty busy. The last few months have been especially hectic given our own submission for Rock Band Blitz, as well as an influx of other devs submitting PLAY / PSN titles for Sony to test. So everyone is jockeying for test time and as a result, older issues sometimes get pushed to the back burner.
The triage priority we've recommended for testing is as follows: delivering new RB DLC -> replacing missing RB DLC -> delivering new RBN DLC -> replacing pricing on old RB DLC -> replacing missing pro upgrades -> replacing missing RBN DLC. These issues were prioritized based on the number of people likely affected, which is why missing RBN songs or pro upgrades may not be the top priority.
ETA of a fix: this info I don't have, but I have a meeting with our DLC Production team this week and will ask them to see if they can re prioritize the Bombtrack pro upgrade with SCEE and make sure it's at the top of their list once Blitz is cleared for take off.
Please trust that we are as frustrated with all of this as you are, if not more so. If we had complete control over the store and could change things ourselves, we would. I hope the above info helps.