quick boss tip:
Baron: Keep pally alive, drain focus or just beat cr*p out of him
Pally: beat him up normally(watch ur focus he heals several times) or subversion
Ignition: heroic motivation counters fate, electro bolt cancles dark regeneration
omen: stun when uses dark omen
doctor: subversion
shadow: keep him without 100focus, luck plays a role here since you misses him often
General tip: level up helps a lot(as well as the glitch)
hope that helps