It takes me maybe a week to level a class to 70, but I need 1 - 3 months until I can play it on a decent level.

You level so fast and because the gameplay is not complete for many classes before you reach 70, and the whole mass pull and aoe it down is more or less a new thing at level cap wich was not that present during the level process, you will not be able to learn how to play before hitting level cap.

Some people, like myself, maybe are just a bit slow with learning. Kick these people from ex trials and savage raid all you want, but how should these people ever become better when you kick them from dungeons and other casual content? Of course some people will never improve, but many others will and they need the paractical training in level 70 dungeons.