I'm a TWC customer, and I used to have consistently horrible YouTube speeds. I eventually got sick of it and read somewhere to try different DNS, as you suggested. I switched from TWC's DNS to OpenDNS probably around a year ago, and YouTube did become faster. It's less consistent now, sometimes loading nicely and sometimes slowly. youtube.com/my_speed claims I'm averaging 7.6 Mbps vs. the average 5.2 for my ISP and 6.4 for the region. I see occasional traffic from 206.111.0.0/16, but it seems to be coming largely from 74.125.0.0/16 and 173.194.0.0/16.