To me, bad players are toxic players. These are players who can't stand others making mistakes, or who call a party trash after just one wipe, never try to give advice, or, if they do, its in the meanest way possible. Also, people who make mistakes themselves but won't admit it. There are more examples, but you probably get the point.

My expectations for dungeons/casual content are super low. As long as the healer heals, the tank holds aggro, and the DPS are at least somewhat competent, I can't really complain. Other content it makes sense to expect more from people.