I have the abovementioned modem that I use for my devices at home. I read on the Battle.net site that to help with lag on Diablo 3 you must make sure that your modems firmware and drivers are up to date.
Seriously I had no idea that the modem needed any update of any kind. I have searched the web and everything I find for Dynalink NZ goes to another site and that site has no info about the RTA1025.

Does the modem actually need to be updated?