Sounds like he is broken beyond repair.. We had a tank like this no matter how much I worked with him he never really improved. It eventually led him to leave the guild because no one would run anything with him.
400 TPS on a boss in kara is down right horrible. Its almost hard to do that little tps.
How well do you know this guy? are you friendly? because you need to be honest with him. Show him a parse of himself and then show him one of yours. Once he sees the evidence then you guys can discuss rotations together and try and clean up his tanking a bit.