Everyone has already given a lot of good advice so I won't repeat that.

What I will say though is have a look at your UI, can it be jiggled around to make things easier? Can you put bars in your line of sight so you can keep up your dps as well as see mechanics? An enemy's cast bar is a good one to start with. It is one of the first things I focused on when I wanted to get into high end content. I do the high end content with my FC and then we fill the rest of the places with PF.