There’s your answer. There isn’t going to be a poor teamwork option anymore, and they clearly defined what is and isn’t reportable in the post.
So long as they are trying to win, you can’t report them. In no way does hero choice prevent you from trying, so them picking 5 DPS is fine. It’s up to you what you want to do from there.
So is the belief that you need a Tank and a healer to win. So is the belief that people should be forced into a role they don’t want to play so that they don’t get banned.