There is one thing that I don't understand Mweb: You are saying that Blizzard changed the way that WoW packets "look" and therefore we are getting latency? (Not 100% sure if I read that correctly in this thread so correct me if I am wrong). Now the temporary solution that you gave us involves us changing our MTU (Maximum Transmission Unit) to something lower and we should not be getting high latency anymore. So in fact we are only changing the data packet size and then all seems well. We are not changing how the packet "looks". Why does this solution work? From what I understood in this thread previously is that the way the packet looks is causing trouble with your shaping equipment and that is why we are getting lag.
Also, have Mweb gotten a hold of Blizzard? Maybe they have had dealings with a ISP that had this fault and know how to fix it.
Lastly, a Latency of 300 - 400 should be the normal latency that we get when playing WoW, because it takes 290ms for a packet of data to reach the edge of Blizzard's network. Any latency you get above that is the ISP's fault. It could be due to bad routing policies, shaping setup incorrectly or even a overloaded or faulty router, but it is something that the ISP should look at.
I mean look at the traceroute below. You can see that everything is fine up until hop 8. Response time jumps from 50ms to 280ms. I assume hop 8 is in South Africa, so 280ms is a bit too high I think. Secondly I play on Aggramar EU, so my server sits in Paris. Look at hop 9. If you do a Geo IP lookup of hop 9 you see that it is in USA. Is this the best route there is for traffic to Paris? Or should I ask, the fastest?
1 2 ms 1 ms 1 ms 10.0.0.2
2 21 ms 22 ms 22 ms 41-132-40-1.dsl.mweb.co.za [41.132.40.1]
3 23 ms 26 ms 25 ms 196-28-178-190.adsl.mweb.co.za [196.28.178.190]
4 47 ms 49 ms 49 ms gig-0-0-2-vic-hscore-3.mweb.co.za [196.22.169.49]
5 49 ms 59 ms 48 ms 196.22.169.61
6 50 ms 50 ms 49 ms tengig-0-0-0-0-11.vic-up-1.mweb.co.za [196.22.169.225]
7 52 ms 50 ms 49 ms tengig-0-2-0-0.mid-1.mweb.co.za [196.22.169.219]
8 288 ms 287 ms 288 ms 196.22.175.222
9 384 ms 438 ms 409 ms 149.6.98.5
10 549 ms 718 ms 386 ms te7-2.ccr01.lon01.atlas.cogentco.com [154.54.36.165]
11 268 ms 272 ms 269 ms te2-2.mpd01.lon01.atlas.cogentco.com [130.117.1.74]
12 285 ms 288 ms 287 ms ldn-b4-link.telia.net [213.248.70.237]
13 287 ms 288 ms 341 ms ldn-bb1-link.telia.net [80.91.249.131]
14 296 ms 293 ms 295 ms prs-bb1-link.telia.net [80.91.247.254]
15 280 ms 277 ms 291 ms prs-b4-link.telia.net [80.91.251.45]
Hopefully someone who is a bit more technically inclined than me can give me some straight answers

Oh, and after the MTU fix my latency is between 500 and 700 (depends on what im doing in WoW)
One more thing, a tunneling service could get your WoW account suspended, seeing as it goes against Blizzards terms of service. That is why I dont use one and never will, so dont even think about recommending it to me...