Um, if Foriel raises his hands like in this video
YouTube - Myth 2: Foriel's 2handed aoe
you either try to run to a safe area, or you basically hug him to get hit only once. I'm not sure about hugging Foriel though. I don't remember it too well x_x
Other than that you can try to use skills with Invincible frames. Maybe Dfist and flying dragon sword work, dunno whether it's enough to avoid all hits.