I'm starting to believe that those who killed him with no problems on the 1st try or 2nd, were lucky or something (maybe that memory bug thing). This boss is the extreme of what I consider a unfair difficulty.
Like you said, after he enrages is where lies the problem... there it becomes almost impossible to parry, and his attacks just gains way more area of effect and do much more damage, allowing him to easily one-hit-kill at any chance. That's just ridiculous...
Sorry, edited... I've not noticed before.
Yeah, I actually can do pretty well until he reaches half HP. Then he becomes impossible to me... =/