This build is a melee, range, and AoE/DoT variant. It is an advanced method to do four things:
1) Provide a fury utility in Weapon Throw that doesn't:
ii) Require tanking in elemental DoT environments -- i.e., Frenzy is great for stacked attacks, but requires stationary monsters to work effectively;
iii) ... limit attack versatility -- you can ranged attack when Whirlwind cannot work on walkers/casters
... and it's great because it:
2) ... extends the Massacre streak (looking at you XP farmers!)
3) ... broaden the Double Tornado's damage utility to lessen downtime between packs;
4) ... provide AoE damage
Why Weapon Throw?
In terms of fury generation, there is nothing better. It's great because once battle rage is up, there's no downtime on fury generation/building. Each critical hit adds 29 fury with the No Escape passive active. Compared to Bash's Instigation -- which is 12 per hit, or other variants, Weapon Throw should be the main fury builder and generation. The utility is so versatile, that it actually does *more* damage over seconds than bash due to no knockback conditions that stalls the damage.
In addition to the above, with No Escape passive up, you're doing 130% + 10% passive weapon damage with Weapon Throw + an additional 39% damage using Mighty Throw rune. Added up, that's 179% weapon damage vs. 165% weapon damage from Bash's natural damage and Frenzy's five stack requirements.
More importantly, it holds a natural slow effect of 60% over two seconds. Hello, Goblins!
To be clear, I haven't really tested this at the lower levels. I farm at MP9 to accelerate my looting (I do believe that the looting system by-passes lower MPs due to the higher MF% -- however, my view on this topic is unreliable because I prefer to see my effort rewarded every run). Lorenze made a good point saying that at 400% MF in lower MPs, you're getting 100 elite kills vs. 40 elite kills at MP9 in the same time frame. I think this is DPS dependent, so consider this a warning not to take my farming choice to heart. I just farm at the higher MPs because it's a challenge to do it faster and faster.
Kick-starting the build:
The key to starting this build is simple. Generate enough fury from taking damage and making melee strike to gain enough fury to get Battle Rage up. Once done, another strike or two should give you enough fury resource to hit sprint on the monsters attacking you. You should be able to generate enough fury from one casting of tornadoes to get Wrath up. After that, it's clear sailing.
On why this build is efficient:
The rule of thumb for farming efficiency has always been one to two passes. At my MP level, I'm using two to three passes or so within different packs to accelerate and accumulate the XP bonuses necessary for a Massacre streak. Rend's Lacerate allows you to deal out DoT damage over five seconds (903% weapon damage) once a cluster has been worn down enough that one sweep of Rend will cause most, if not all, to die. This five second window is what Alkaizer used in his paragon farming runs to build up such large streaks and be the first to hit Paragon Level 100. One could conceivably use Ravage for wider AOE, but I find that unnecessary most of the time because I want to utilize the extra 203% damage since most trash will have descended on my position anyway.
In addition, it's great for allowing players the option of spamming Throws for range damage against casters/walkers and DoT damage on them as well to continue carrying a massacre streak. Rend is an EXCELLENT anti-elite AOE DoT damage skill.
The No Escape passive allows continuous fury generation of up to 29 per critical hit, meaning that one or two taps of Battle Rage and Sprint will quickly reset the Wrath timer, allowing you to carry on. What hasn't been tested is how much critical hit chance is necessary to endure consistent fury generation.
Permanent wrath is NOT an issue. Mob density is the issue. So I have revised my route to go through:
Keeps 3 --> Keeps 2 --> Fields of Slaughter --> Rakki's Crossing
I keep this short and sweet.
I would welcome different routes for other considerations if one could come up with a great one that differs from Alkaizer's route.
Boohaha's summary on the play-style and whether it is worth the gear investment:
I thought I would add my $0.02 to Acrimony's post, perhaps explain some of the theory and practiced playstyles to those who are unaware or do not have the gear to test this before seriously investing:
I made an earlier post about Throw/WW barbs, essentially is a WW barb, but uses throw weapon as a fury generator instead of the traditional generator.
Seismac slam VS. HotA VS. Rend
For those wondering the effectiveness of Seismac slam, HotA, or Rend, I would say Rend is the most effective. As a traditional throw/ww barb (perhaps, we can coin a new term called "Throw Whirldwind" or Tww) Rend (lifesteal or increased damage) is very necessary because no matter how much you fear (echoing fury) or slow (throw weapon inherently slow, or cold soj) phase beasts and ubers will always be melee range. That being said, Rend (lifesteal) will allow you to tank melee range and elite/uber AOEs.
Seismic Slam IS fun. There is nothing more satisfying than doing a huge almost-1-million seismic slam crit that one-shots everything it touches in a wide cone (20 monsters killed in 1 hit). However, when you face any elite able to close the distance, your seismic slam will often miss many of the mobs and hence, Rend's pointblank AOE (PbAOE) is much more effective.
HotA I have yet to try.
300th spear and it use
Someone also mentioned 300th spear. The moment you swap your offhand from godly-offhand-of-stack-stickiness to 300th spear, you will be using throw weapon as your main damage doer because the stats of 300th spear are, at best, subpar. Not to mention the 1.2 attack speed (compared to 1.3 for axe, 1.4 for sword, or 1.5 daggers) will not allow you to WW effectively. You can still WW and keept WotB up (I occasionally practice this) but it is difficult and I am watching my fury orb more than the actual fight.
Throw Weapon as a fury sink
What I suppose would be more efficient is to (someone mentioned this earlier) use weapon throw as a fury sink (instead of spamming Sprint and Battle Rage) by using either Mighty Weapon rune for damage, or the Hammer rune for stunlocking. With all your IAS gear that you WW barbs use, spamming Hammer for stunlocking/slowing ranged elites allows you the time to run up to them to do your serious WW business. It also has a fast animation compared to something like Seismic Slam, and hits for almost-as-hard without knocback. Knockback is annoying if you are a WW barb.
Throw Weapon as a fury generator
As for fury generators, which someone mentioned earlier, I believe that fury generators ARE a crutch if you use them to generate fury (weird huh). However, if you utilize fury generators for their rune's effects (Frenzy's Maniac rune, or Bash's um..... same +damage rune), then the utiltiy offsets that low damage of fury generators. From my experience, I believe that weapon throw may be the #1 fury generator because of its insanely high damage (for a fury generator) is RANGED (htiting ranged elites that kite you, hitting MP10 ZK while he sits in his bubbles, hitting MP10 Magda while she sits in a corner with 5 arcane lasers around her) and extremely high fury return.
An effective use of Throw Weapon as fury generator
Therefore, I may bold in stating that for any WW barb (or the most effective build for very-geared PvM barbs), the most effective fury generator (as somoene had mentioned) is to use Weapon Throw (Mighty Throw or Hammer rune) combined with passive No Escape and your Battle Rage (Into the Fray rune) to shoot fury generation up to 29 per crit (100% proc ratio on weapon throw's Mighty Throw and Hammer rune). Given high end gear; 50% crit ratio and 400% crit damage, you big hits and big fury regen, thus increasing your fury-regen quality of life. It's also ranged - it slows or can stun if you rune it that way. It is only single target, but when you face MP10, you're mostly only aiming to hit the boss anyway. When you are doing elites, your normal WW/Sprint will AOE everything else down.
Other builds as effective as Tww (throw whirldwind):
Someone mentioned using HotA. Although I have yet to test this, I do not think it is as effective as WW simply because WW ignores unit collision. This implies being able to WW out of dense mobs that force you into arcane lasers or molten explosions on MP10.