<<If the D800 shot DX mode at 8fps we would probably be having a different conversation here.>>
Yes we would, I agree. However, if you have file sizes on a monumental scale of the D800, then the buffering of images to memory card is a problem. The D4 has 10fps shooting with AF and AE, 11fps with focus and exposure locked. That's a totally different camera with advanced processing power. The 12.1mp D700 (5fps, 8fps with grip) and the 16mp D7000 6fps.
The D800 shoots at only 4fps or 6 in DX mode (which to me is acceptable in DX mode).
One can't have everything and technology comes at a price. I would prefer two bodies, a D400 and keep my D800 until someone proves to me it's as good as it's cracked up to be.