Port Strobe, I suppose the "big picture" answer to your question would be how likely would it be for the same airplane to suffer what amounts to three separate electrical failures within one flight (the APU gen is deferred, then both IDGs fail in sequence). The "no man's land" scenario you're describing would last approximately 8 seconds (I suppose those could be the longest 8 seconds of a pilot's life under the right circumstances), which is NOT long enough to justify flying around with the RAT deployed, in my view.