I believe there is a large difference in ping related to server location. Here's a useful link:

http://www.wowwiki.com/US_realm_list_by_datacenter

Going from Deathwing in Boston to Tichondrius in Los Angeles, my ping went from 150-200ms to 15-20ms. I live in Orange County, CA, which is neighboring Los Angeles.

I have a friend in Australia that said his pings went from 500-600ms on Deathwing to 250ms or so on Tichondrius. If I were you I'd sign on a few and see what difference it makes. You might find yourself a better match that way.