The area you were referencing to earlier, isnt behind the walker, isnt in a corner of the room; but is in the middle of the area where the second saturation fire lands. It is an exploit in my eyes based off the fact there isnt a plausible reason why you would be safe in that spot. I have come across that spot on a few occasions in the past, when i was slacking and standing in fire, and felt that it was odd that i didnt get hit.
Line of sighting the Gift of the Masters, isnt much of an exploit, based on the fact that doing so usually gimps the raid dps in some sort and actually making the enrage a little bit tighter. You're trading a situation where more healing will be needed with a situation where more dps isnt needed.
EDIT: Found a video
of what i consider to be an exploit in this fight. You can see a decent example of it at 2:27