I've played World of Warcraft since Kel'Thuzad (original server).
Never had any issues other than WoW server side issues, that was back in the days.
I've played WoW, and WoW: Burning Crusader both on Charter cable and AT*T old DSL line, never had any issues.
I did know that AT&T years ago had problems with the WoW routing, but that was a while back, and the issue was supposed to be fixed.
Regardless where the server is located, you shouldn't have any lag issues.
I'd suggest posting this matter in this World of Warcraft forums (Tech Support) I am sure they can troubleshoot this issue better than we can.
Also check your router settings.