I mean it is mostly a symptom of a bigger problem which is: The game has a terrible feedback loop.
You quite literally have zero way to tell if you are playing good or bad, the game doesn't help you or challenge you in a way that would make you rethink your rotation. Someone could play Ice-only BLM until max level because the game won't ever tell you that's wrong, or have you fail because you are spamming Ice spells only.
This is a serious problem, because the moment someone DOES tell you that you are playing wrong, its a big shock, and a lot of people don't handle this shock very well. But can you blame either person? It sucks having people who don't pull their weight constantly hold a group hostage because no one can say anything to them. And it sucks trying to learn and feeling lost/overwhelmed because you have to go off the game to learn how to be better in the game.
Yes having a public meter would lead to an increase in toxicity, but just crackdown on it more harshly. They can afford to hire more gm's/mods to do this, but making meters so convoluted and hush-hush to get is denying a lot of players, specifically console players from having any way to learn and/or improve. Which simply doesn't work in a game where there is very difficult group content.
If the devs don't want players curating other players, then they need to put in work to make the game do it instead.
Numbers are useless unless meaning is put behind them. Seeing that most people are playing RPR/MNK right now won't really tell you the why behind it.
RDPS/ADPS/NDPS don't exist anywhere in the game or combat log. These are metrics that exist soley because of FFlogs, as such, the devs have the data on their end, but what can they do with it? There is nothing wrong with them using FFlogs to determine balance. I find it to be a good thing. But it is def a thing that happens, I'm like 90% sure of it.