If you struggle to log in close the battlenet app go into your game directory under _retail_ and click on the wow exe. wow will open then enter your username and passwords manually make sure you have your authenticator once you do log in and you on the char screen but cant see your chars and the background is black just wait n while it will appear and all will be good after that. This is what has been working for me and most of my guildmates.
Weird thing is, that when you finally login there is no lag, even on Wednesday evening in Boralus.
2004 and dial up issues are really unexpected... or are they?