After building a new Web Application (a simple one-pager actually) with VS 2015 Rev 3, then publishing to WS 2012R2 IIS 8.5, and creating the simple rule in Forefront TMG to allow the site to be visible to the public internet, the site does not respond / times out.
Fiddler on the gateway machine where TMG is based states that all 200's are being returned for the page, and there is no access issue. When browsed from inside the private network, the URL is obviously going through TMG (port 80 is returned, not port 99 which is how the web application is setup internally).
I've been working on this for a day-and-a-half, and have pretty much had it. Other existing websites are responding without issue, even on the same web server.
I can only think this has something to do with the publishing process for IIS 8.5, or something to do with VS2015 Rev3, but I am hoping that someone out there has had an identical issue and resolved it.