Yeah, sure. Let's take a 4K costing camera capable of 8K raw and test it in 4:2:0 mode while saying that you shouldn't expect it to perform as it's not a dedicated videocamera. Well, then stop marketing it as an 8K raw video shooting camera, Canon. Those overheating issues were preprogrammed in such camera design. Can't cram 8K raw recording into a small body without any way to handle the heat. Simple as that. So was this the marketing plan? To give a taste of raw video but just a bit, and then shut the door in front of you :).
Amazing... A new camera with old specs of 8bit 4:2:0 still gets attention for video in 2019?! Only Sony can pull this off... Like the claims of 15+ stops. For stills maybe. But for video in 8bits?! Seriously, guys, does anybody still believe this crap. The only mirrorless cameras worth mentioning for video are Fuji X-T3, Nikon Z6 and Panasonic S1, given that S1H is still covered in mist.
Enable 10 bit 4:2:2 over HDMI, then we talk.
Tested D850 for video when my wife bought it as a photographer. At first I was very sceptical, but then it sort of grew on me. Even the full frame which I never considered before, S35 size always seemed perfect. Was looking for some DSLR size camera for small fun projects, and D850 does look good. My finding was completely different - it looked the least video-ey of the bunch. Yes, rolling shutter is quite bad, but workable. The detail is excellent, and no oversharpening like in some of the other photo cameras that shoot video. This is a fine example: https://vimeo.com/258781771