I have just completed this at level 54 with gear level 104 and it was extremely tough.

One thing i did do was buy some super potions from the Market this helped a little to use these whenever possible.

Make sure you only fight the main boss with full combo and all cooldowns prepared (bloodbath and second wind) also keep using Third eye every 15 seconds.

You will want to move around avoiding his attacks as much as you can whilst your cooldowns rotate, Meiki Shiysui is essential and keep your buffs up!

Be sure to combine Kaitan and Midare Setsugekka when he is paused doing his cast moves for maximum damage.

It is really tough but I am a noob to the entire game not just SAM and did not buy any gear for this besides the potions so it is doable..!

Took about 5 attempts. The key is to keep moving and using those cooldowns.

Hopefully this will help someone..!