MVP forum poster Lissanna posted an interesting walkthrough of her own attempts to find the culprit today, and explained why despite some forum poster dissatisfaction that it is indeed helpful to run a traceroute and pathping and post the results to the tech support forums, since it gives Blizzard an idea of who to talk to about these issues. If they don't know who's being affected, where those people are, and more importantly where the issue is physically located there's not much they can do to help.
So if you're having the same problem, giving Blizzard as much information as possible is definitely helpful in terms of getting this sorted out. I've seen people in my raids disconnect on every single boss so far while I haven't had the issue at all myself, suggesting the problem isn't on Blizzard's end but is out there somewhere in the path the data takes between Blizzard and the players. Hopefully it can be solved soon.