I'll ask differently.
If the DVR records.... the stalling or buffering doesn't happen to the recording because it comes in from the modem to the router then to the switch then to the Shield then thru the Switch on the NAS and stays there.
Once it is recorded and I watch it, My devices are connected to my router so my client asks for the file.... thru the router, to the switch, to the Shield which takes it from the NAS. So from the NAS it goes to the switch then to the Shield then to the switch then to the router then to my client.
My point is.... wouldn't I see the same problems while watching a recorded show on the NAS?
By using a USB HDD all I eliminate is the Ethernet to the NAS. How is that different than it going via USB to the HDD?