Quick Left AF Test Validation
I don't think you should worry. Do the experience many times with all the sensors, and you'll find out that the camera never exactly focus at the same point. Fine tune your lens for every point and report the numbers that you get. A difference of 5 units is within the specification.
Also, move back a little bit. A distance of 5 feet would be better for a 28mm lens. And get good lightning conditions. All of this will lower the difference you get in between 2 consecutive shots with the same AF sensor.
Most likely, your D800 is fine. The D800 affected by the left AF sensor problem were way out on this sensor. Thom Hogan says that is was impossible to get the left AF point correct with AF Fine Tune.
Thanks for posting the pictures.