Your traceroute is completely and entirely unhelpful (please
read this to understand traceroute), and even if I had source/destination IPs, I'd still point out once again that Youtube/Google using
anycast, as well as multiple layers of load balancing (both GSLB and DNS-based) across thousands upon thousands of servers and networks across the globe. That makes this very difficult (bordering on impossible) to diagnose. I will also point out Youtube actually does a form of rate-limiting in their Flash applet as well (though it's a logical design -- it would take me probably 2-3 pages to explain to you how it works (or seems to)) -- but this is not the cause of the issues.
Again I will repeat myself: the claims in the referenced URLs is that by filtering/blocking outbound packets to nonsensical network ranges, "you can fix the problem" because "TWC is throttling connections by sending web browsers to their own caches" -- and I have yet to see hard data (read: packet captures) proving that. Packet captures can/will prove or dismiss that specific claim.
What you're effectively asking me to do is to teach you nearly 15 years worth of networking troubleshooting knowledge, and without access to both endpoints (yours and Youtube's servers/network), and without access to any engineers in between. It's just implausible.
All I can tell you is that Youtube "being slow" is a universal problem, and has been for quite some time, regardless of ISP, and regardless of streaming service (twitch.tv/justin.tv, Ustream, and a couple other places regularly experience the same thing). I have even had users tell me
"Youtube works fine on one of my systems but not my wifi/mobile phone!". You can read his conclusion (see his last post, last paragraph).
I see "Youtube slowness" periodically as well, throughout all hours of the day. I have some theories as to what's the root cause is, but it sure as hell isn't my ISP (Comcast). I've seen the same from twitch.tv/justin.tv at times, as well as other streaming providers. I only have so much visibility (see above), but the reality is that the Internet is something that is broken 24x7x365 for multitudes of reasons and is basically a "hobbled together" best-effort thing where solving real problems involves actual engineers and lots of red tape + money + time (the latter is the one nobody seems to have).
You can dig around online looking for other claims of slowdowns/etc. and you will find them ad nauseum for years now. Yet none of these people appear to have the low-level technical knowledge needed to actually diagnose this problem correctly -- instead what happens is people making wild claims/accusations and coming up with snake oil "fixes".
The only "workaround" that makes sense is using a VPN/proxy service, and that
does not mean your ISP is throttling you, it means that you then begin shoving packets through a different router/take a different path to reach your VPN/proxy provider, then they shove your packets out a completely different router/path than what your (non-VPN'd) connection would be. Do people really think Youtube has a single network connection, a single server, a single *everything*? Sigh.