I have this issue and I was told by several people that it is based on the enemies casting. If you are still in the red affected area when the skill is done casting, you will get hit regardless if you run out of range because technically the skill is already complete, they are just waiting for animation.

This is what I was told, it sounds logical but I don't know if it is true or not. I get by AoEs that I am not in a lot. I am usually with a good healer so they can still keep me alive. Sometimes it gets so bad that I just stop dodging all together, why should I waste time breaking my rotation to dodge when I am just going to get hit anyways? Might as well take the hit and keep my dps going.