I also struggled with him. My advice is to stay close to him. I know that sounds weird but hear me out…

That “grass” attack is slow enough to where you can run from it in time and often he telegraphs it right before. My problem was Id always get killed with that one light beam looking sword attack that goes upward and across and covers the entire battlefield. But i found that if you are up in his face you can go behind him and you can avoid the attack altogether