Beat Cold as Ice on 3rd try. Used the following skills:
Defy Pain - Sever Artery - Gash - Galrath Slash - Tiger Stance - Ebon Assassin - Restful Breeze - "Finish Him"
Once he summons his spirits I ran away. Obviously since it's impossible to fight with them around. So get out of range, he'll follow. Then rush him, summon assassin. Once he summons another Shadowsong cast healing and run away. He regens but not too quickly. Get out of range. He follows, summon assassin attack...rinse repeat..you should kill him after about 3 or 4 times of running and healing and attacking.
EDIT: Using consumables like cupcakes would probably make it a lot easier.
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