This aim to assist with bombs placement on heroic difficulty.
This requires your tank to ensure the boss has always 3 holes nearby.
The direction is dictated by the icons that dbm / big wigs use on these players.
Star = front (Usually near the tank).
Circle = left
Purple = right
Boss dictates where the front should be.
Left leg as left looking from behind.
Right leg as right looking from behind.
Dont want to deal with icons / dbm / mark assist setup?
Try the stand alone version here (thanks to alethasis!):