I wonder if it's my card cards (6450 and 5450) that are the reason DXVA isn't working. Passthrough seems to be working fine otherwise (5.1 U1) but ofcourse I can't passthough USB controllers or HID devices.
Sounds like you have a pretty nice setup. Do you pass the hub to the VM or the individual devices 1 by 1? Also, what motherboard are you using?