Uber Exarch does massive amounts of fire damage. With enough skill you can dodge most of it. But I'm not a skilled player and this build requires very little skill. For this particular fight I swap Zealotry and Unbound Ailments for Arctic Armour and Purity of Fire (move Clarity to the gloves). And take out 3 damage supports from the Cyclone staff to avoid killing the minotaur too quickly and losing the source of leech. There is also the 'Less Damage Taken per 190 Intelligence' blue implicit on the chest, and Immortal Call. With all that mitigation I still have to Frostblink sometimes if the boss uses Annihilation or Cleansing before 50%. And after 50% all the damage vs Low Life kicks in and he dies quickly.

PoB snapshot of the character in the video: https://pobb.in/zv2l_Ou4M9Th

Build guide: https://www.pathofexile.com/forum/view-thread/3294484

Music: Casey Rasch - Premonition