I would say about 90% of the time they target my Zuul’goth, and the other 10% they just randomly hit whoever, could be front target, weakest target, my hero, I don’t know. When they do kill Zuul’goth, I just restart, because I almost never see boss slayers in Mini-Boss or Mythic Boss so restarting is faster.
Also I switched out Doomed Axe for Doomed Crossbow. It does color block Zuul’Goth, but Glaycion converts yellow to Blue and fills up Zuul and Doomed Crossbow turns Blue into Skulls so it’s a good synergy after Glaycion. Overall much faster team.