I also used the shotgun method much like Neverwintermoon.
Soon as I entered, started pumping him full of shells while backing away slowly into the corner next to the door you arrived in. Once he was close enough, I made a run for the opposite corner. What also works is timing his swing; as soon as he begins the swing motion, I made a run for it. Was not hit. This gives you time to reload or recover from any blows taken.
This was done on hard mode.