I'm fairly sure that there are other factors involved as well. I often have 1/5 clients with noticably higher ping than the others. My setup is 5 clients across 3 wired machines. My guess was that cpu/memory(keep in mind client memory leaks/bloat over time) constraints caused additional latency occasionally. With standard variances that networks predictably encounter and host-specific factors would likely cause wow to register one client as worse performance than others.