The build utilizes Power Siphon of Archmage CoC to cast frostbolts, it is also the trigger for Fanaticism from Instruments of Zeal, I also linked mana leech support for mana regen and cold snap for frenzy charge generation and chill ground.

This build has a rigid rotation, you have to count "1 mississippi" (not kidding here, this is actually what I do) to cast Power Siphon to generate Fanatic Charges.

For mapping and general content, I use Greatwolf, but for delve and bossing the reflected reduced projectile speed amulet is invaluable.

The build is 6k delve worthy, but not tanky enough in its current stage.

PS: I didn't have the full ramp for the first 50% of the boss hp bar, what I should have done is to get Fanaticism before engaging him.

PoB: https://pobb.in/GJ8exL4vR-JB