I imagine that may also be a reason there is little traffic in the Open Class Forums - for those that never make it to a World Class corps, they probably feel their opinions, or the topics relating to Open Class, won't be valued so much, so they fly under the radar instead.
And as far as using Open as stepping stones to World, I read a recent online discussion where at least one of the Open Class corps members attacked those who leave the corps for World Class, which I thought was rather an immature comment to make. Until you are in Drum Corps, you cannot have a good idea what it will really be like in general, let alone specific to that corps, yet that person expects people to remain with their first corps (regardless of the reasons they chose it - proximity, $$$, heck even uniforms!) not just for the first season, or two or three, but for the person's entire corps career?