There are three steps you need to take to make it work.
1. Modify your hosts file under \Windows\System32\drivers\etc\hosts and add the following entry:
127.0.0.1 mydomain.com
2. Turn off your proxy dection from the IE,
Go to Tools->Internet Options->Connection->LAN Settings, uncheck everything
3. Modify your binding in the IIS manager to use mydomain.com instead of localhost as host header.
http://blogs.msdn.com/wenlong/archive/2007/08/02/how-to-change-hostname-in-wsdl-of-an-iis-hosted-service.aspx
BTW, you need to remove the quote here.
So instead of
cscript //nologo %systemdrive%\inetpub\adminscripts\adsutil.vbs set W3SVC/1/SecureBindings “:443:www.fancydomain.com”
you shoud do
cscript //nologo %systemdrive%\inetpub\adminscripts\adsutil.vbs set W3SVC/1/SecureBindings :443:www.fancydomain.com
Hope this helps.