Would you be opposed to SE implementing a program to scan for addons/parsers?

[Kazhar]

uh? Sounds like cope. Here is how you know if you are failing because of dps: you cleanly handle all mechanics and understand fight, yet die to enrage timer. The enrage timer is literally the in game feedback that tells you you're not doing enough dps.

This is fallacious in a game with 8 players. People who say this have either no experience in high end content or are being willfully blind to the facts. You could be playing perfectly but still die to enrage timers if one or more people on your team are severly underperforming. Similarly, you could be one of the worst player in the game and still get carried hard. So no, beating enrage timers doesn't tell anything at all about your own performance, just the performance of your team. But in a game where a large portion of endgame content is done through pugging, at all level of play, one team's performance means absolutely nothing. You can't always count on others. And I certainly hope you have better standards as a team player than "I'm doing just enough dps so the enrage requires perfect play from everyone else."

Dps meters aren't "performance enhancers", they're feedback. You don't always need it especially if you happen to know how to play your job already, but personally I wouldn't leave it to chance and feelings. Logs are cold, hard, facts which can't be disputed.
I don't care that some people raid without it (most of my static don't use ACT and they're good players), but whenever someone says they're great at the game without once looking at any kind of feedback I'm asking myself "how would they even know?".