well all i can say is this game is a ***** even on easy
that xeno has a proximity based ai routine as far as i can tell.
it's not based on if it heard you or not it will go to your general location regardless if your being quiet or not and it will roam somewhat (but only after basically hiding from it for about 5-10 mins) on a side note it isnt incredibly observant, if you end up being in its view for about a half second or maybe 3/4 of a second even if its facing you it a lot of times will not notice you and will continue on its way; but damn if it does! reminds me of the speed difference between a cheetah and a dog running away last all of 2.3 seconds before you get a tail through your gut (which i must say i was not expecting when i thought he was about 10 feet or so behind me)
[Edited by Mechcondrid, 10/6/2014 3:35:57 PM]
They are incredibly fast, same speed in the open and in the vents.