Lagon's beam picks which direction it's going to travel when his eye turns red. If you understand how it pick the direction you can move the other direction right then and it will just sweep away from you and you just don't need to worry about it.
It will always sweep to the side of center that you are standing. So basically, when you see the eye turn red, start moving towards the center and you shouldn't have to worry about it.
Best thing to do is just get a SC character there and practice the mechanics.