In my case the situation is really awkward. I am also using the BCM94352Z card. The trackpad works perfectly. The mouse not so much under OS X however, guess what: works great in Windows 10! I am using 4K with both OS'. At this point I'm kind of lost. It's clear that is not the mouse (dirty, etc.) and it has to be something else. Changing the type of surface improves the tracking in macOS Sierra however using the same surface that causes issues in macOS works great in Windows 10. Very weird.
Did any of you have a similar experience?
EDIT: I think I found the root cause for the mouse misbehaviour. I have a desk pad (an old one) made by IKEA and it looks like it's made out of some sort of metal covered by faux leather. The mouse pad was on top of the desk pad. As soon as I removed the desk pad (still using the mouse pad) the mouse moves like I just bought it now. This finding is really weird since it doesn't explain why the mouse was working great in Windows. Who knows, maybe the mouse was being affected by the desk metal pad and the macOS is more sensitive than Windows, or Windows gives the PCI WIFI/BT card more power? I have no idea, however bottom is that removed the desk pad seems to have solved the issue. I will keep using it this way and update my post if I see any change.
EDIT 2: After a few days of use I can confirm that the IKEA desk pad was the culprit. The mouse has been working flawless since. What is interesting is that I have not noticed the stuttering with Mavericks or Yosemite. Not sure what has changed since - if any.
