I think it's the community's and the streamer-s fault for the "OMG they nerfed the beam/Bounties suck now"- reactions. The community learn from the streamers that the way to play the game is to push it to the limit of efficiency. Proc coefficients wouldn't be such a hassle to balance if people weren't making exploity CM builds that nearly breaks the game.
Also, streamers contribute to the notion that the beta is a chance to play the game early. They think blizzard hands out beta keys and say "We like you so you have the privilage to play before everybody else!". IMO, streamers are not necessarely the best beta testers. I'd rather see people who already have contributet with tons of feedback to the game. I'd bet Kongor plays the beta for "dat twitch monaaay" and won't be handing in any valuable feedback.
I used to play a MMO called Tibia some years ago and I've participated in many test servers. They have a very good testing process.
Firstly the developers make the content and announce the content patch/update. For about a month or couple of weeks they let the "tutors" and highly ranked players (similar to MVP) test the content. When they test the content on the test server, they have allowed people to access the new items/features from the start so people can start testing right away.
For example: Are there new weapons or armour added to the game, you can get those items from a testing NPC for free so you can't start testing it.
And when they have had their time communicating with the devs, they let open up for the public test server.
All in all, I'd rather see valuable players (like MVPs) test the beta before streamers take it out to the public. They should also focusing more on demanding feedback from the beta testers and make it clear that the test realm is for testing.