Do you have any firewall(s) installed on your computer? Have you tried disabling these before gameplay, to see if they're interfering with your connection attempts?
Ensure that you have the latest firmware installed for your current modem (this may be difficult if you can not identify it's make/model).
Please download PingPlotter
. Run it, and perform a search to: us.logon.worldofwarcraft.com
-- Once it is finished, click on 'Edit', and then select 'Copy as Text'. Paste the results here.
Also, please run a tracert -- Start
--> type CMD
and press OK
--> type: tracert us.logon.worldofwarcraft.com > C:\traceresults.txt
--> Please be patient when waiting for the tracert command to complete, it may take several minutes. When you are returned to the command prompt, then the trace is complete (ie: when you're able to type in the command prompt window, it means you'll be finished -- so just press the 'D' key every minute or so). Once it is finished, navigate to the text file C:\traceresults.txt, open it and copy/paste the results into your next reply.
Finally, depending on your OS, please restart your computer into Safe Mode with Networking, and then try to play the game, to see if you still experience the lag whilst playing.