You can look at it both ways. You are on a linear progression throughout the raid, so as you enter the room and move forward, Oryx is at the front. Everything else is behind you as you move forward. Or you can look at it like, i entered through the door at the front and moved back towards Oryx, making him at the back of the room. I personally think Oryx is the front but hey, tomayto tomahto, potayto potahto.