At the end of the array mission, while I was getting destroyed on hard over and over again lol. I noticed on the 2nd level there is an out crop or computer desk like section with 2 extended monitors. If I jumped on to that section ground based AI would not be able attack, instead they actually hid from my cannon fodder and waited patiently for me to jump back down. Air based AI however were still able to attack me no matter where I tried to hide. Also there was an ogre trapped in the cliff in old Russia @ the helicopter crash site I wish I had more info or you guys but I missed the boat thinking it was just another shitty game... Boy was I wrong!!! Bows to the new god of the gaming Universe BUNGIE