Re autofocus, the 6D is better than the 5D2. There were plenty of wedding photographers that switched from the 5D2 to 6D.
The reason you see comments about it being poor is that when it was released the main rival to it was the Nikon D600 - I nearly bought one, glad I didn't as there were a raft of issues with it, hence the arrival of the D610. The Nikon had loads of focus points. Hence people slated the 6D. This never bothered me because most of what I shoot isn't going anywhere. The centre focus point is very sensitive and I use back button focus with that point. So focus and recompose.
The GPS allows you to geotag your images so you know exactly where they were taken. The wifi allows you to control the camera with your mobile phone as a remote with live view.
As for video, all cameras come with it, some better than others.