the SLD parameter is being ignored, defaulting to the symbology as is published in the service. I cannot seem to make any SLD be applied as a GetMap parameter in ArcMap 10.1 (or in partner's services which are in v10.2). I can however force the SLD to be applied as a GetMap parameter from a service hosted on ArcMap Server v10.0:
Is it just a coincidence that the SLD is not being applied to any 10.1 and 10.2 ArcMap-published WMS? Or perhaps someone has come across cross-domain issues, where ArcMap upgrades might have created some web server, Windows, or other issues which is disallowing the web-accessible SLD to be read from another web domain?