DXT is extremely lightweight compression designed to be decompressed in parallel during the rendering process. 10mbps is plenty if you're using a video codec, and the Pi has hardware H.264 support.
Are you sure about that? As I understand it you usually don't want to have more than 4-5 B-frames in a row. And if you use baseline profile you eliminate B-frames and can cut the latency to be less than a frame.
