What I was trying to say but was not understood is that, in photographic practice (as opposed to internet tests), it is much easier for me to get smoother highlights on my H3D than my D800. The reason is not that the DR of the sensor itself is higher (it is sufficient for both cameras), but that the camera meters are calibrated differently (I already adjusted the D800 meter down) and that Phocus is optimized for that task. Nikon apparently chose to optimize their cameras for better low light performance, it is an area they compete for.
Thew D800 offers a +/- 1 stop optimal exposure fine tuning in the setup menu independently for the three exposure metering methods.. Matrix, Center weighted and Spot.
On top of that there is a 5 stop exposure compensation that cam be done while shooting outside of the menu. This is a total of 6 stops adjustment and should cover any compensation you need to move exposures to the left or right of the histogram.
In theory, we should expose to the right. In practice, as opposed to theory, we tend to oversaturate a small range of pixels by doing so and don't notice them as they are too few to show on the histogram. These are the values needed for the smooth high tones that the O.P. is seeking.
It can be easy to miss a a small area of pixels that are oversaturate (clipped). However there is a handy way to check on the D800.
Review the photo on the LCD and display the histogram. Then zooming in on the image the histogram is calculated only on the zoomed in image
and it animates in real time as you move around on the image. I use this function a lot when shooting makeup with glossy or metalic eyeshadows.
It's great for any shots where there are small hotspots that you don't want to clip.
When the histogram is calculated for the zoomed in image the small areas become much more evident on the histogram.
Also if you go into highlight clipping warning mode (the one that flashes on and off) even the smallest clipping will be shown.