I do agree with you on that, about DPS being the hardest job in the game to play correctly. However, you must also take into account that DPS is also the most accessible out of the 3 roles, being the one with the least responsibility. I have kicked bad tanks and healers, as I am sure everyone has. But, you must also take into the fact that the community curses bad tanks and healers more than it does than DPS, despite DPS being only 1 job, and that people have access to the Internet, where you can at least learn the basic rotation and practice on a dummy.
I do agree with you that, when playing to a high standard, tank and healer is the most easiest roles to play (especially healer), but I digress. The point that I was trying to make that those who are tanking/healing are treated much more harshly than DPS, so while tanks and healers can potentially get better, DPS don't get the criticism or have accountability in their actions to improve. It's much easier to clear content with acceptable tanking and healing, than with mediocre DPS to try and clear content, because the game is disjointed from its levelling phase and endgame phase, where there's no real way to highlight what areas a DPS needs to improve in.
But as tanks and healers are very noticeable in how they operate, I'm pretty sure it's safe to be certain that it's much easier to see any of them under perform, and it's much more easier to call people out on it as people are much harsher towards them in general.
