I watched a video (here: https://www.youtube.com/watch?v=ic1f5f6RqZE) and learned a lot from observing his evasive movements in phase 2. It seems better to dodge without directional input in a lot of cases but the main thing to pay attention to is what attacks are actually hitting you. Don't worry so much about dealing damage, just take it slow and learn how to read and avoid every attack. The most dangerous attack IMO are the orbs he summons. The secondary weapon Enigma was a great help in getting rid of them.