u can get the ping value from WOW interface, there is a small bar with green,yellow or red color.
green = low latency
yellow = medium latency
red = high latency
and also, pointing on this bar will give u the ping value (like 200ms)

anyway, as long as u can play the game without lag then don't bother about the ping value
sometime the ping value not that accurate.

enjoy ur game, its a good game