I read some where that the “lag” is actually being caused by the new CoherentUI process they added/updated in a recent patch.
This lag is different from the normal “skill lag” you get in large zergs. That appears to be on the server side. This lag appears to be on the client side. I say this because some people experience it when others at the same time say everything is fine. Ping tests are fine, so it doesn’t appear to be network related.
To test the idea I tried hiding the UI in game (CTRL+SHIFT+H by default) and all of the lag went away. Everyone I had do this also had zero lag after doing so.
Of course the problem with this is that you can’t reliably play wvw with no UI. You can’t see commander tags or maps or even your heatlh/dmg. So it’s not really a good fix if it does work for you.
I don’t normally post on the forums but if this IS the issue and this fix DOES work for some people then hopefully the word will spread and Anet can fix it.