I'm also very close to completing the Kanai's Cube legendary extracts (Video attached below of my stats) I completed Season 20 100% with this build without much difficulty to be honest. I put this together during the Season 20 play (IK was the Set reward) and am currently around 720 Paragon while posting this (yes, I know that isn't very high) but enough to say I'm on the highest tier today (TXVI) and feels like i'm 1 hitting many mobs when my Frenzy stacks and unlocked Primary Ancient drops by completing Greater Rift 70 (GR70) solo. I have not seen any build's specifically for Barbarian's wearing the Immortal King's (IK) Set gear where the Primary Skill is Frenzy and Secondary Seismic Slam. This non-static effect rotates through the elements available to your class in the following order: Arcane, Cold, Fire, Holy, Lightning, Physical, Poison.

Gain 150 - 200% increased damage to a single element for 4 seconds.

Stat Priority: Str Armor + Skill: Frenzy Pickup Radius.

Stat Priority: Str Vit AR Skill: Frenzy.

Stat Priority: Str Vit Life Pickup Radius.

Stat Priority: Str Vit AR Pickup Radius.

( 2) Set: During Whirlwind you gain 30% increased attack speed and movement speed.

Diablo 3 immortal king set build