I am a bit curious as to when the problem started and in what way do your newer images fail. When you first got it and used it on June 18th you made comments below excellent BIF images:
"First day with D800 in the field. AF-C autofocus is better than my former D7000, D300 and D200. Very happy with results"
"D800 focus test. Random bird flying 20 yds away. D800 in AF-C mode followed this small bird with ease. More than 9 out of ten shots in focus."
What changed, lenses or shutter speed perhaps? Post some images that fail to meet your expectations and still have the exif data intact and maybe the forum can give some advice.
With LightRoom or others in your collection of software, pixel peeping at 100% or more is a tougher test to pass than with lower resolution cameras so are your complaints about prints the same physical size and viewed at the same distance?
When you say the camera is sluggish, are you referring to time to empty the buffer or actual camera responsiveness? The camera is faster in shutter response time than others you mentioned so that must not be it. The AF is certainly fast, but possibly a little slower than the D4 but better at tracking moving objects than your other cameras. So what specifically is slow about your D800? If a camera deteriorates as you say this one has, there is usually a reason that can be rectified. Please post some recent images that show what you are referring to.