Betas ARE for playing the game. You are expected to play the game as you would in release. Only difference is that your expected to file bug reports and attend events. If you are not power leveling, trying to find exploits and creative ways of doing things, you are not helping. Leveling speed is beig watched to tune its speed, exploits need to be passed on to dev just incase they have not caught them already and if you find things are too easy or hard, pass them on for dev to tweak before release.
Only difference between open and close betas are the NDA and who is invited.
Headstart is not Beta, we have the game as it will be at release, it is however pre-release so some things still may change. hopefully it will only be behind the scene load balancing, networking and procedure finalization.
Ya know, I hate to be the antagonist in a flame war (well ok I guess not really) but I've got to say that if more  actually used Open Beta for it's intended purpose and actually tested the game as well as reported bugs rather than power level or use the Beta as they're own personal "I wanna play the game" time..we might not have so many damn bugs now.
Me? I read every line slowly and took in the story, I tested and tried things in the game to see if they worked or didn't work. I reported umpteen dozen bugs and faithfully did so. I get the feeling many didn't.