The description for Polearm Mastery states that staggering an opponent places it at the end of the turn order. However, this is not the case: it merely lowers the opponent’s initiative. If that opponent is a high-initiative opponent (e.g. necrosavant, direwolf, wolfrider, mercenary), it may still be ahead of you in the turn order and still be able to wreck havoc and/or apply stacks of overwhelming before you can fight effectively. This greatly diminishes one of the few strategies that makes Polearm Mastery seem like a worthwhile option.