As the title says, Team voice should be the default rather than Group. If you want teams to interact, this is how to do it. Many players I've run into either forget to switch channels or are too lazy to change from Group.

We had this implemented at one point but let me explain why we ended up changing it. The majority of the time parties are formed it is on the main menu. When you're on the main menu, there is no team chat channel available because you are not in a game. So the first problem was that it felt super awkward to join a party and then not be in team chat. Obviously, we made it so that the default was to join party chat when you joined a party but then we tried switching you (as you recommend) to team chat as soon as you joined a game. We quickly discovered that switching voice chat channels on players was very jarring and no amount of interface/sound warnings made it ok. So we ultimately opted to set the defaults as they are now.

Just to follow up, we definitely want to encourage positive team communication. My answer earlier wasn't trying to state that things are fine. I was just pointing out that we had tried forcibly switching voice channels for players and received extremely negative feedback for doing that. What we would like to look into is trying to make players more aware that team chat is available and encourage participation.

I'm not confident forcing players into a channel will actually solve the problem of "people are not talking". I play the game a lot -- solo and grouped -- and it comes down most of the time to people not talking (even when they are in the channel). Maybe they are shy? Maybe they have nothing to say? Maybe their mic is not working? We'll try to help with all of those issues but you can't sledgehammer other players into talking over the internet... you can only gently encourage...

Since the time of this post, there is now a one-click button in the Hero Selection screen to switch or turn on Team (Blue) Voice Chat.