Ok an update for anyone that's interested...
At this point I would guess that installing the latest Dell drivers inc touchscreen etc now probably wouldn't cause any issues as when I did the exact same procedure with my Asus T100 i.e. installing driver updates that seemed to cause issues BEFORE a full factory reset but now afterwards on a clean Windows 8 install the T100 has been trouble free ever since.
With all this mind does anyone think there is any chance that flashing new bios / firmware files on Windows 8 tablets with connected standby doesn't actually ever make the same changes / fixes as when done on or before a new install?
My best guess is that something gets stuck / not updated and will never fix itself until Windows is factory reset which if others having similar issues on their Venue Pros can try themselves then maybe we might be closed to be able to providing a fix for everyone?