I think you are confused about the severity of the tradeoffs between f/8 and f/16.
Diffraction exists on today's cameras at f/16 and f/22. But if you are happy with those images, it's not enough to be an issue. Others would avoid those apertures due to diffraction.
On an FX body at 16mm, with a subject 2 feet from the lens, a DOF calculator shows a hyperfocal distance of 3.55 feet with an "in focus" range from 1.28-4.51 feet. At f/11 your hyperfocal distance is 2.5 feet with a range from 1.12-9.39 feet. At f/16 the hyperfocal is 1.8 feet with a range from 0.95 to infinity. So we are talking very small differences due to a single stop.
With the D800 you lose about one stop to maintain equivalent diffraction to the D700/D3.
Now with the D800 you also pick up a sharper in focus area with more detail. And if you ignore diffraction, you will probably have something very close to a D700/D3 - it's just that you won't realize that extra sharpness.