"With the seperaters we can also hook up four singles (311's) with the use of two seperaters"
According to DISH's PowerPoint presentation on DP+ technology, you can not do the above as suggested. Their presentation states that a DP+ twin LNB can only support one or two DP receivers without use of a DP34 or DP+44. The dual-tuner is considered a single receiver in the above statement.
If you are hooking up 3 or more single tuner IRDs such as (311s), you must use a DP Quad or switch.
Have you ever done a 522/811/311 install? If you have, you know then that a DP+ Twin is no good and you have to use a DP34 to accomplish this install. According to your assertions, an installer could do this configuration simply by putting the separator at the demarcation point for the 811 and 311.
One could further argue that an install that consists of a DP+ Twin and a (2) 311 IRDs would only need one coax run from the dish and the separator again at demarc. This is simply not the case.