The orbs wouldn't spawn for me either. After a few tries, I actually got it done... by the fight bugging out completely, and not even triggering the 2nd phase. The NPCs kept on hitting him until he was down.
Had no companion up, and stopped attacking the boss completely as he got close to where he threw the NPCs against the pillars the previous time. The NPCs took him down to about 10-15%. Then I had to finish him off when the NPCs started dying off one by one.