I am having the exact same problem that the OP described. But I'm using a WebAfrica unshaped account.
I came across these articles though.
http://wow.joystiq.com/2011/01/07/the-lawbringer-lagpocalypse-2010-2011/
http://community.virginmedia.com/t5/Broadband-down-your-phone-line/World-of-Warcraft-Latency-Issues/m-p/161857
As far as I understand it's the way the packets are being sent since 4.0.1 it is seen as P2P packets and that gets throttled by South African ISP's to hell and back.
Blizzard states that they are collaborating with some ISP's to resolve the issue but unfortunately those are US ISP's.
I came across these articles though.
http://wow.joystiq.com/2011/01/07/the-lawbringer-lagpocalypse-2010-2011/
http://community.virginmedia.com/t5/Broadband-down-your-phone-line/World-of-Warcraft-Latency-Issues/m-p/161857
As far as I understand it's the way the packets are being sent since 4.0.1 it is seen as P2P packets and that gets throttled by South African ISP's to hell and back.
Blizzard states that they are collaborating with some ISP's to resolve the issue but unfortunately those are US ISP's.