Great answer and I love the explanation, but here's what causes me the problems, that is I have to work out on the fly every couple of seconds what is the optimal thing to do, whilst simultaneously dealing with the bosses mechanics, calling out stuff and performing my encounter specific role (stand in the puddle, get on the belt, vigilance the tank, whatever). To be frank I can barely keep up
Sometimes I feel that I have to bust my guts to keep up with some other dpsers , and by the end of the raid I'm physically drained I'm in awe of the performance of some, and can barely comprehend how they do it.