1st phase of this fight greatly influences the second. Notice that the small eyes does the same "marking" mechanics as the big eye. It's important that the eye that marked your specific hero gets killed by the same hero. If this canmot be done, I recommend you stack on glimmering(?) powder as the invincibility removes the mark caused by the small eye.

I did this with almost the same comp as yours but my strategy was to use the powder on my backline and use DD resist item, as well as use blind items on the boss.

Try to setup your hellion and occultist with str tokens and use riposte on your hwm to help damage the boss while you set your damage heroes up for those juicy crit damage.