Weird. I've not yet encountered a monster where the red circle wasn't perfectly in sync with the action you had to avoid. The thing I've noticed, through practice on my gladiator, is that the red circle, NOT the enemy animation or cast bar, is the only thing you have to pay attention to. Any time I've exited the red circle/cone/rectangle before it vanished, I've not been hit, and running back in before the subsequent casting animation goes off (but the circle is gone) means I don't get hit by the attack, even if the animation goes through me. It's a bit counter intuitive, but it hasn't been much of a problem since I've gotten used to it.