greg, I cant speak for comcast, are you using docsis 3?
I use comcast at home, 2 hd tvs on all the time have several machines on the net and levi is around so youtube and the playstation is constantly downloading gigs of shyte with no issues or errors except the occasional loss of dns at 6pm weekdays. It doesnt appear to have any issues at my home. Dont know why your market is different
They are blocking and trying to inline DNS requests.
Docsis v3 isn't quite supported here yet, the equipment and the cable lines here are 25 year plus old... and are getting cranky causing tons of bad things.