I'm actually running some WD shows, due to demand and the fact that I like money haha.
What I've heard from judges is that the tests are judged exactly like dressage, but in western tack. It's only a matter of time until that sport is "un-winnable" without a big fancy warmblood like how regular dressage is now. And you're allowed to use a curb two handed.
The whole thing is really poorly thought out, IMO and needs some serious rule revisions to attract and reward stock breeds and western riders and not alienate them when BNDT on her big fancy warmblood two handed on a curb comes in and wins everything. It needs far more separation from normal dressage. Right now it's just a chance for those on horses who win in normal dressage to go win fancy prizes in a western saddle.
They say money doesn't buy happiness -- well happiness doesn't buy horses!