This is one of my big complaints about the app store too. I've had one user get a refund on my app, but Apple wouldn't tell me why or give me any way to understand what happened. All I got from Apple was the boilerplate, make sure you app doesn't crash etc...
One thing Apple could do to make the app store a much better experience for developers is to set up some type of communication exchange between the developers and users. They could still keep it anonymous, but when Apple issues an update that breaks my app and then takes over 10 days to approve my 1 line of code fix I'd like to let my users know that it's out of my hands.
I have also tried adding my direct email in the app and have never received an email from a user. Admittedly, I have a lot less users than you do though.
One thing Apple could do to make the app store a much better experience for developers is to set up some type of communication exchange between the developers and users. They could still keep it anonymous, but when Apple issues an update that breaks my app and then takes over 10 days to approve my 1 line of code fix I'd like to let my users know that it's out of my hands.
I have also tried adding my direct email in the app and have never received an email from a user. Admittedly, I have a lot less users than you do though.