This is my first post here and I registered specifically to be able to write this reply. It seems to me a good deal of the softness complaint I'm seeing has to do with mistaking photographer technique with camera performance. This thread is a case in point.
The original dog picture may be soft for reasons other than dpp settings or focus error. A moving subject with a long focal lens, an aperture of 5 and zone autofocus is not the best condition for great sharpness. The depth of field is too shallow, and the angular shake due to following a moving target with a long lens can produce a lot of blur.
On the other hand, the sharpness of the Nikon portrait pose as an example is taken in a controlled environment, with controlled lighting producing subjective sharpness. There is enough DOF to put the whole model in focus. Also, the skin texture hints at a good deal of sharpening applied (something I'm not too crazy about personally).
As someone else said, I have a number of portraits with L135, that look just as sharp (at least at that enlargement ratio), and the camera attached to the lens is an old 5d classic ! On the other hand, when I shoot moving subjects with my 200/2.8, I know I have to have a speed 1/1000 or 1/2000, to avoid any kind of even minute motion blur. The dog picture here is taken at 1/500 if I'm not mistaken. Too slow, and with the shallow depth of field...
There may or may not be a softness issue on some 5diii bodies. But we need to run tests in conditions that allow for the best possible sharpness, in terms of photo technique, before we can draw any form of conclusion.
