Recently I've went from Brazil to New Zealand and tried playing on same realm... I was amazed at first, my ping in NZ went up from 200 to 1k, but it was understandable due to distance... But I was even more stunned when it actually dropped, in less than 1 hour, back to 200.
When I came back to Brazil, the ping took just few minutes to adjust.
Now, that proves to me WoW itself already do a lot of ping optimization. So, I wouldn't bother trying too much other things as you can most likely disrupt its own system than help your ping.
The best thing to do is definitely tweaking your own machine for optimizations. Things like what people already suggested here, such as the Leatrix (thought it really didn't work in my case, on wifi) and getting a cable if you are on wifi.