When you get the Light Essence buff before the fight you can use (buyable in brd) to imitate the orbs hitting you and stack the powering up buff before the fight starts.
See what happens is that when you have the Light Essence buff ANY fire damage will give you the powering up buff , so you can stack it to 99 before the fight then get the Empowered light buff right at the start and get an extra boost in DPS right at the start of the fight, very helpful for the hard mode fight.
This also works if you're a warlock and cast hellfire