I'm only a level 39 BLM at the moment, so I can't pitch in TOO much about higher level fights.
But it is extremely annoying that we need to interrupt 1/3 or more of our spells do to having to move around. It's either that or take damage, and if you take too much damage, you need to sleep them and cure yourself up. Really the only way to move and still cast if if you are at the very last few seconds of your casting time.
Otherwise, I don't have too many complaints, it's a pretty straightforward job. I can't say that we are out damaged too much, as in a party I usually fall 2nd after tank and sometimes third.