I used to joke that the only reason I'd end up in closed beta was because they wanted to figure out how to nerf my powersets without anyone noticing but then they figured out that I adjusted myself and not the build
Seriously though, if you look at what I'd do in test and what I've "/bug"'d, it made no sense to include me in beta.
1) I don't have the time to test everything new 20+ hours a day. For that matter, I don't have time to test for 2+ hours a day.
2) The stuff I'd find would be things like grammar errors, incorrect vector values, missing particles, etc. Hardly the stuff you'd want to know about when you're wondering if a Cold/Cold Defender is going to break the games "balance".
3) I don't play conventionally. Quite frankly, the dev's aren't as concerned that I can solo any archtype. I'm sure they'd have concerns if I could do that in less than 40 gaming days but we all know how much effort goes into preventing that. Really, in this case, I'm wasting their time.
The bottom line is to truly be a contributing beta tester, you pretty much have to be devoted to making the test subject the best it can possibly be. Simply wanting to be in beta is not good enough. You have to be good enough to basically push the subject to its limits to try and break the thing AND you have to be diligent enough to record and report what does break. It's not ONLY about having fun.
To be honest, I didn't care for being in past beta's. It felt like I had to be responsible for something and that I was a disappointment when I didn't break anything. Don't get me wrong, I hit the open beta's as soon as I can so I can "preview" what's coming. However, to be in an actual beta felt more like a job and that is so opposite of why I play games in the first place.