If you're having trouble with this boss, go in with your Amitra charge at full, and try and carry at least 5 Elixirs.
This was my 7th consecutive attempt, so I made quite a few mistakes out of frustration.
Mid-stance worked best for me.
In the ball & chain phase, there are 2 kinds of attacks. For the frontal ones, stay close and roll towards him under the arm that isn't being used (if he's about to swing his left arm, roll into his right). For the sideways sweeps, keep your guard up and move away.
Ki pulse is essential as all this will drain your Ki very fast.
Attack the horns for Amrita.
In the no chains phase, stay away and double tap the dodge button often to roll away. His range is vast and he hits hard in this phase, so simply evading won't be enough. Follow up with rolls are crucial.
Look for openings, but don't get greedy. Ki pulses and purifications are tempting, but time consuming. If you're not within direct line of his sight, he will violently sweep towards your general direction and if you're guard isn't up, you'll lose a large chunk of life. Stay infront of him and dodge roll. DO NOT TRY TO BLOCK THE BALLS, THEY WILL HIT REGARDLESS.
Fully charged Amrita can be a game changer, but try not to get greedy as I did.
Patience is key.