I've been having the same issues as you guys, the problem started with the server merges.
Server: Ebon Hawk
ISP: Virgin Media
Today I've managed to completely resolve my server lag, first I enabled Multicast Pass-Through
on my routers firewall settings. The second thing I did was go to http://www.opendns.com/business-solu...m-dns/benefits
, create an account and follow the instructions, it takes less than 2 mins and you don't need to download anything.