Mobs in PoA seem to 'see down the corridoor' regarding aggro... At least in some places, and only once disturbed (ie a puller working at the end of the corridoor). It's as if the aggro follows the pathing paths.... Also, mobs tend to go 'backwards before forwards' and vice versa when following pathing in several places.
And yeah, 15 or so of the armoured dudes is funny.... Less when they appear as 1 at first.