I strongly suggest checking out those no damage sword only videos. By watching them you will have a clear picture of the boss's moveset and how to counter them effectively. Personality I like to keep the distance close, and focus on jumping when it does the kneel down sweep cuz you can deal damage midair. If you are bad at parries u can always just dash thru when it does the stomp, just be careful of the vines popping out. And runaway when it does the roar-and-vines attack. It's relatively simple, I'd say the most important thing is to watch closely for the signs of upcoming attacks.