I found a way to counter this, even if you are lagging.

I play as a Paladin, so i noticed something, and here is what you have to do, and you won't be hit by AoE:

When you see the red AoE ring run out of it and when you are outside of the ring, make an attack on the boss. This way i think the system registers your position that you are really outside of the ring and you won't be hit. I have not tried other classes but i think it will work for them too, maybe it does'nt need to be an attack. I know that casters are in disadvantage because of the casting time, but try this: When you see the AoE ring start casting a spell which is not interrupted by moving, run out so when the actual spell is shot, you are outside the ring. You have to time it right, but this tactic worked for me after i discovered this.

Try to spread this information, and make a feedback if it works for other classes in laggy situations.