Dear GM
is it a bug ? when players stay the platform. they don't worried the attack of Bloodlord Mandokir.only need the tank stay and attack out side of the platform. if you think the behavior is a bug ,please fix it;
if it's a bug ,i think you should take measure to penalize them for their behavior.By The Way,i watched the player is an anchorman. his action maybe let more player to exploit the bug;
Lastly, the players were punishable by rule?