when you are fighting him, and his health gets low, he absorbs a dragon soul, does he then use it to respec his stats before switching weapons and attacking you??? also why dont you learn the shout he uses to absorb the dragons soul, like you learn the dragonrend shout?? what shout does he use? i read it in the subtitles during the fight but i dont remember what it was and didnt recognize it from the vanilla game???

If you can go back and get the words, I can see if UESP has their translations.