If this fight starts with the Boss having two helpers in a relatively small room. Use Backblast on the helpers, to soften them up for easy kills. Keep moving between the corners, if a server is lowered, raise it from cover.
Pour it on into the boss as you hop between Servers, he actually goes down easy since he's a soft target (unarmored). Its the regeneration that is the issue with him.
Now if its the fight in the large Atrium, that is a whole new can of worms.
Even with the 2 helpers killed, there is no way I can whack the boss. Tried diffrent weapons and still cannot kill him.
Is this the game bug?