And how would that harassment change?
Without (official) parsers:
"Dude, you know you're bad, right? And you should feel bad. Please put in some effort so you're not inconveniencing everyone else."
"Hey, I *was* trying, man."
"Hardly felt like it. Your threat was *really* low even without using Diversion."
"Uhh, maybe because I died. You dropped that freeze AoE on me, remember?"
"No, I didn't. And it was low even before that. And the Bard half his aggro, twice, after I rezzed you, and you still never got close to catching up."
"Whatever man."
"Whatever? Your rotation must be ****."
"And?"
"Learn your class. Before you queue into stuff. You've had 70 levels to learn it, so quit procrastinating."
"Dude, I know my class. Why don't you play your own?"
"Mate, I play mine and yours and all the others. And a lot better than you do. Probably most people can say as much."
"Prove it. I'm waiting with a GM ticket."
"I'm not about to get into that. Just.... please... learn your damn class."
With parsers:
"Dude, you know you're bad, right?"
"I mean, I have the same data you do, so... sure?"
"Please put in some effort so you're not inconveniencing everyone else?"
"Hey, I *was* trying, man."
"You shouldn't be getting such low numbers in that case... Your rotation has to be seriously off."
"And I'm working on it. But it's hard for me to open with my CDs still on... CD, from the AoE pull before boss."
"You've got other ways to ramp up quickly than PB, man."
"K, but it's still confusing for me. My damage is all over the place. I can't do anything with what's completely random based on the run."
"Look, just... look at your toolkit and breakpoints. The rest of us are making do just fine. You've got Form Shift and Riddle of Wind. Use em. If you can't get used to it in dungeons, pretend your cooldowns aren't ready yet when punching a dummy and check your numbers that way..."
"Yeah, screw you too, man."
"Screw you too."
[Message blocked.]
Tbh, people tend to be more dogged when there's a chance for ambiguity, either in the verity of their claim or in the target's knowing its "truth". All else being the same, people are less likely to start a conversation, berating or merely critical, with someone they can tell is underperforming
by choice. Whether they suck themselves into harassment thereafter or not is probably much the same, but at least the frequency is reduced a bit. And let's not forget we already have parsers, and anyone likely to go off on an underperformer as enabled solely by a metric making detection more convenient is already going to be doing so.
That's not to say you can't have aggressors without parsers. Not remotely. I had someone go off for my rotational choices as Monk despite his being outperformed by every member of our 3-of-4 roulette premade (yes, the tank and healer, too).
Actually, every player who's ever gone off at me or a friend in my party has done so from... not a great standing. When a new healer thought he had screwed up and I said we simply didn't have the damage to do the pull (as evidenced by the fact that nothing was even half dead by the time I'd exhausted every single CD) and I shouldn't have bit off so much--that he was doing great and I just need to stop clinging to how I run with friends--the two dps bffs proceeded to harass me more than fight for the remainder of the run. And then for the ~20 minutes after the run until I blocked them.
I've yet to see numbers come up even in critical speech outside of raids. Where it's come up, it's either been about mechanics, complete lack of AoE skill usage in AoE situations, lack of external toolkit usage (Tactician, Refresh, Goad), or has gone so far as to mention exactly what's wrong whilst offering advice.
"Hey. How am I doing, if anyone's got a parser?" on the other hand? At least a dozen times. Usually each really friendly runs. Information and responsibility =/= toxicity. If anything... it tends to foster community. Just, a community that prides itself on helpfulness rather than the right to burden others (because their 1/n portion of the composition must surely be worth the rights of all n combined).