HoTA Base Fury Cost: 35
HoTA Fury Cost with Unbridled Rage: 70
Whirlwind Base Fury Cost per second: 25
Whirlwind Fury Cost with UR per second: 50
70+50 = 120 Fury per rotation
120 > 100 - Required to proc Red Ring
WW 2 seconds
HoTA Crit
WW
HoTA Crit
WW
HoTA Crit
Etc…
Alternatively, Whirlwind for 2 seconds = 100 Fury. With your Fury Generation and Enhanced Whirlwind, while you will have used 100 Fury, you probably have gained close to that amount back if you have hit enemies.
Whirlwind starts channeling the second you hit the button and stops the moment you release it. You can literally tap it and hit another Skill like HoTA and it uses the Fury from Whirlwind and counts as a Weapon Swap for Earthstriker assuming you have it bound to somethi else.
120x3 = 360 Fury, or a guaranteed Overpower from Banished Lords Talisman on your next HoTA. Whirlwind for 6 seconds also procs Banished Lords as it will use 300 Fury. Tibaults and Metamorphisis + and sources of Unstoppable will help you gain Fury super fast.
This lets you start fights with Banished Lords, Bonebreaker, and ES swaps all very easily. The set-up is what causes Barbarians to be able to one-shot Bosses and World Bosses because with Red Ring, your OPs will be Crits amplified by Vuln and Berserking.
It is poorly thought out by Blizzard.