As far as I know, a D800 with the grip it's a 6 fps 16 mpx D400 class body DX camera.
Great landscape camera in FX and not a bad wildlife camera in DX. If you need both worlds it's not a bad deal.
That's not the case, the D800 is faster if one shoots in crop mode, but only in jpeg… If a crop mode is used with Nef (raw) files, only buffer capacity profits positively. Never the less, all wildlife serious shooters, either pros or artists that are publishing their images or exhibit them, are using FF cameras… (one can check that on web). Same happens with serious sports or reportage photographers. Obvioulsy, the high-iso advantage of FF that helps them freeze motion is more important to them than being able to "reach" at longer distances through a cropped sensor. Lets not forget that the combination of a VF with poorer visibility and extra distance, decreases capturing ability a lot and the extra bockeh of FF sensors, also helps for better images. Another thing to consider, is that smaller pixels also require better lenses, which of course rises cost… (some never mention this). In fact, the 300mm f4 which is quite popular among "long-reach" users, is better than the new 80-400 when used with a TC-14eii attached and is usable at full aperture (600mm f8) with even the TC-20Eiii attached on all FF cameras, but with a high pixel density DX, the use of TCs (especially of the TC-20Eiii) makes quality suffer…