Thing is, a dedicated video camcorder is gonna have issues handling that shot as well, if you are in dark enough light where you have to shoot at f/1.4 or f/1.8. I know my XA-10 ($2000 camcorder) could probably handle it, but, it would definitely have some noise, and even there the auto-focus isn't perfect. When I film classrooms, it guesses which kid to focus on and can miss focus in darker rooms.
It's always a compromise. I can't even take useable pictures on my XA-10...so its a big trade-off to get auto-focus that certainly isn't perfect.