So general reply to this thread. Meant to put this up last week, but got busy - sorry, all.
After several patient requests for escalation, I finally got a reply. Here's the meat of it:
"I have results on investigation. Apparently , this is known issue to Surface which there currently investigating to fix this issue. There's no estimated time is to when will the issue be fix."
Microsoft Support is leaving my ticket open. It would seem that Microsoft has now at least acknowledged the issue.
So it's disable power saving on the Qualcomm for now. On the positive side, at least Mike helped us all get to a workaround. :)