It seems to me that Microsoft hides the links to these forums. You can find them on the Microsoft site, but they are buried under a drop-down list with about 100 other forums.
Some people are still using the forums at BizTalk Gurus: http://www.biztalkgurus.com/forums/
You can post a new question/issue to the MSDN Community Forum here:
When you select “BizTalk Server” fro the “Forum category”, you will then get the list of specific BizTalk Forums on the right, as shown below: