Everyone, as far as I\'m concerned the question is ansered in EDIT 2. Although it\'s only a partial solution to the IIS side of the problem, it\'s what I was looking for.
Just for someone else who may look in the future. We upgraded to Windows 2012 server and IIS 8. The old config compression mimetypes which worked for IIS 7 did not work for IIS 8.
So, I tried a couple of suggestions here, but nothing worked. I ended up just adding this to httpcompression dynamictypes: multipart/* and then gzip compression was working again.
Hope this helps someone else.