Just based on my own observations and experience (mostly over a decade of WoW), these are the general issues with parsers / DPS meters:
  • Parsers are CHRONICALLY misused and misinterpreted, very few people actually use them properly. More often than not, they're just used by people to stroke their own egos.
  • More often than not, parsers enable harassment and other bad behaviours. You have to remember, jerks don't need a good reason to bother someone. They just need an excuse. You'll instantly see a lot more people call others "bad" under the flimsiest of excuses than see anyone take the time to analyze and advise how to improve performance, far more harassment than constructive criticism & assistance.
  • Moving into the more subtle psychological effects of parsers, they push the community to place a lot more value on performance and subsequently the culture becomes significantly more competitive... and it's not the friendly type of competition either. As noted in the previous two points, you see a lot more misuse of the tool and abuse of other players than actual benefits socially.
  • A very subtle one, but players stop paying attention to mechanics or even outright ignoring them in a bid to increase their performance on the meters. While both matter, measuring something tends to make it a lot more important to person doing the measuring for some reason.

While this game does have DPS checks (actually quite frequently, though those in the default difficulty for content are quite generous and usually restricted to intermission phases)... the developers have made it perfectly clear, they don't want people to obsess over the damage output. It just causes too many social issues.

We're here to enjoy the experience, not squabble over someone's performance not being "optimal".