Finally SUCCESS!
Everything Dish tried (2-LNBAs, full cable rewire, duo-node, receiver) did not solve the 1-2 second blink outs of sound and brief pixilization. So I looked inward having already replaced the HDMI cable.
It appears that my TV, a Sony Bravia KDL-46Z4100 (and probably the KDL-40Z4100 baby brother) had a sound blink out issue and issued a firmware fix for it. I tried the new firmware and had no success, so I removed the HDMI cable and went with component cable - problem solved.
I have to give Dish a lot of credit for sticking with me during this elongated period of "search and destroy"!