Really? Did you read the post? All of it? To the last sentence? Really?
I am not using DHCP for delivery of the PAC/WPAD file. I have a DNS entry only, no DHCP. The DNS is hosted on AD 2012R2. The WPAD web site is on a Ubuntu 14.04 Linux box that does nothing else. The only thing on the website is the wpad.dat file in the root of the site - hence the web browsers working. All OS are set to Auto Proxy Discovery - not pointed at a URL and do not have explicit proxies configured. I have even tried setting the index for Apache to the wpad.dat file. If you browse to http://wpad.<insert domain here> or just http://wpad/ you get the wpad.dat file downloaded. The only things I have set in my DHCP scope is the default route, time server, DNS server, and DNS Domain Name.
You might not want to rely on Wikipeida too much. WPAD does not default to anything - it has to be configured in DHCP or be configured in DNS. If you don't do either of these, nothing happens. In my case, it is configured in DNS.
Reconfigure? Can't, nothing to change.
Retest? No point, nothing changed.
Open to suggestions.
Oh yea, almost forgot - I have the required mime type active in Apache for WPAD.