This could actually be due to DNS, rather than anything particular to that edge-cache/CDN. Resolvers that aren't actually close to you (network-wise) could cause problems like this, or TWC partitioning their network in a way that causes geographically diverse locations to get lumped together, etc. In essence you'd be talking to edge-caches on the wrong edge, so to speak.

To test: try a different DNS resolver, and see if you start getting faster video loads. If you're using TWC's local resolver, try 8.8.8.8 (run by Google); if you're using Google's already try the local resolver and/or OpenDNS (208.67.222.222).

If that does work as well, I'd recommend it over the heavy-handed approach of blocking arbitrary netblocks. Especially since that second netblock listed isn't owned by Google, and so you could be collaterally blocking other content that you still want.

(Disclaimer: I work for Google, but in Ads, not anything network or YouTube related).