You are at least 113 posts short, just look under the first post that started this thread. You will see he has 87 posts as of the writing of this post.
Beta testers wonāt have any affect on the vision or direction of a game. All beta testers will do is report bugs. They would never be able to influence good or bad decisions. Not really.
I think what you mean is focus groups. Now they would absolutely affect the direction of the game, and Blizzard needs to be very careful in their selection process.
Call it whatever you like. As long as there are dedicated gamers who test the game before release and their feedback is seriously taken into consideration, major design aspects could get changed.
What testers can NOT influence however is marketing decisions. That is why we donāt have to worry only for D4 devs, we have to worry for D4 marketing team too. Itās getting more complicated than D3 for sure.
Google what a focus group is, in relation to game development. They donāt operate that way, and they can often do more harm than good, depending on the pool.