So trial and error... don’t do like I did and pick the left side which gives damage bonus but is lessened with the more players you have in the group.
I didn’t realize the other side stacked and is insanely good for us. Each rank gives 50 insanity to the entire group. With a full 5 person group that brings your base insanity level from 1000 to 1750 (almost double!) .
Needless to say I feel a bit behind now and am going to work on that section now.