Dilbert, you are misunderstanding "inconsistency."
The 50 Art can be perfectly calibrated, yet still misses focus on too many shots.
You get your AFMA perfect, then you get into a shooting situation, and one shot will be just right, then the next three will be terribly front or back focused. I know--that is exactly why I sent mine back.
After trying for 10 days to get the 50 Art to function properly, I went back to using lenses that do work, such as the ef 85mm 1.2 L (so I know all about shallow DoF) and the ef 24-70mm 2.8 II L. WHAT a FREAKING relief to have sharp, accurate, 95% successful AF!!!
Dilbert, do you understand now? The 50 Art, for whatever reason, can be perfectly "tuned" to match a body, and still be all over the place. If you happened to get a copy that does not exhibit such behavior, stop trying to tell others that there is some kind of user error or misunderstanding.
And, btw, I have a 35 Art that is almost as reliable with AF as my 24-70 (the best AF I've ever seen), and a Sigma 15mm 2.8 fisheye that is spectacular. Those work. I think I made a mistake buying the 50 Art before Sigma, using its customers as testers, figured out what is wrong with their production.
As for the USB dock, it might make things worse for Sigma customers, because now there is this extra level of trouble-shooting Sigma tech support can use to delay actually finding out the true problems with their lenses. Customer calls Sigma complaining about erratic AF, Sigma asks, "Have you used the dock?" Customer buys dock, gets frustrated, return time to merchant has expired...Seems like it will cause more problems than it fixes FOR THOSE CUSTOMERs WHO KNOW HOW TO AFMA IN CAMERA.