I'd also say that if you're looking for good video performance, you definitely want to look elsewhere. The mirrorless world does pretty well in video, especially Panasonic & Sony. Even Olympus is better at video. Canon would be the only good DSLR for video. It's probably going to be a long time for Pentax to catch up in the video department.
As far as AF performance in the DSLR world goes, Nikon seems to be the king for the most part. In the battle of the flagship pro models, the Nikon D5, Canon 1DX, Nikon D500, & Canon 7DII pretty much rule the AF area. However, even Sony is catching up with the new A6500 mirrorless. Olympus is also catching up with the OMD E-M1 Mark II. But yeah. They're all extra pricey. Out of the higher end APS-C models (D80, D7200, K-3II, A77II), Nikon still has slightly better tracking AF.
I'm really hoping that Pentax will at least equal or pass the AF performance of the Nikon D7200. I'm not even asking for much 'cause the D7200 is already "old" & will probably be replaced in a year or 2. The next D7xxx will probably blow away the next generation Pentax APS-C flagship at AF performance once again, though. It's all relative.
But yeah! If video is definitely something that you want to do, take a look at the Panasonic & Sony mirrorless cameras. I'd say that Panasonic is probably the king of video in the mirrorless world. I'll probably get tarred & feathered for saying this, but I really do think that even the A6500 will blow away the K-3II at AF performance in just about every respect & does video as well. However, there is the price tag.... Hahaha! There there is the whole issue of not enough Sony APS-C lenses, the wobbly jello like video, blah, blah, blah,................ & so forth & so on. You give up something for something.