Let me bring a new point to this topic: Parser is a tool that prevents wipes and as the result prevents morons from getting offensive. Because morons will stay morons, I would even argue that it removes as much toxicity as it adds.

If the players see their own performance, they are better equiped to improve their skill. Better skill means less fails due to dps checks. Less fails means more players clear content without problems.

Group parser also tells you how much effort you have to put in the fights. If there is number x that the group has to do, then you might feel motivated to try harder to avoid failure. Right now you have to wait for the fails, which could be easily prevented if you knew group's output during the start of the fight.