Don't know how it's possible, but it got worse. Ping starts out OK for about 20-25min, then spikes into 1k+ territory, almost always resulting in a claymation scene, followed by an inevitable crash to desktop. Can't do anything with this utterly terrible connection status.
EDIT: before you ask, yes, the problem is unique to GW2. I stream and play other online games just fine with no service interruptions.