Jason,
The only issue with DMA disabled would be high CPU load, if that does not affect your application, I think you are ok.
I just looked the usbmon trace which has one encoder. As you said MSC runs fine in this case, but in Line 5622, the encoder sent a video frame which size is 15686 bytes, which is way much bigger than normal size - around 1K.
Then the controller sent a SETUP packet (Line 5654). I have to check the UVC Spec to understand what this SETUP packet means. This is not something I use in my daily work, I am unable to integrate it right now.
