Goal: A low attack-maintenance, "lazy" Barbarian with exceptional mobbing, survivability, and team utility, at least at non-Inferno levels of play.
Cleave: Frankly, I think Cleave is a no-brainer for many builds. Bash remains a decent skill, but knocking back is unfriendly to this build's concept. The Clobber Rune on Bash (35% 1.5s Stun) is notable, but may be too much clicking for the Lazy Mobber. Frenzy appears far friendlier to dual wield focused builds, as Frenzy only increases the attack speed of Frenzy. We're going to be using a Shield and One-Handed weapon as most special attacks appear to rely on the main hand for their calculation, unless they are of a special type and hit multiple times. For Cleave we're looking at Rupture for the added aoe capabilities with the thought that Cleave explosions will soften nearby enemies for the meat of this build, Revenge. If this isn't feasible, Reaping Swing (+Fury) may be a good choice, but this is a cooldown-build, not one that requires constant Fury spamming.
Rend: Oh, Rend. Radial area of effect (just like enemies will spread to attack you) and a dot effect. Whirlwind is another alternate that I've waffled with between several builds, but Rend in this build, despite being the only real fury spender, is your filler and it has superior life-leech capabilities (9% of all damage as Leech) than Whirlwind (1% on Crits). Hammer and Seismic are non-starters given their directional aoe. We want to be surrounded.
Ignore Pain: Ignore Pain's filling the role of your "must have defense" choice. However, given that this build has a healthy amount of defense otherwise, this in practice may be replaceable by a more functional positioner like Leap (i.e. Leap into a pack of twenty bodies, begin combat with your optimal position, Leap to ranged targets, etc.). I went with Ignorance is Bliss as the rune (20% damage as Lifeleech) with the thought that IiB timed with heavy Revenge use could refill your entire lifebar several times over.
Revenge: Alright, here's the essence of the lazy mobber. Revenge procs at 15% (30% with Provocation) when you are hit by any amount of damage, costs no Fury, has no cooldown (that we know of, as far as ICDs go) and deals as much damage as two instances of Whirlwind. For more fun? It gives you 5% health regen per enemy hit. At a 30% chance, the odds of a pack of mobs not lighting Revenge up for you dwindles pretty low.
Threatening Shout: We want enemies to hit us so we can Revenge spam them, but we certainly don't want them to hit for more than we can regen with our Revenge/Ignore Pain/Rend. Threatening Shout is a bit of an upkeep as you're going to be casting it every 15 seconds, but is actually a Fury generator, so as long as you have a second it's a boon to you to cast it. Rune choices are a bit awkward for the Lazy Mobber and Threatening Shout, as mobs that are debuffed Movespeed or Attack Speed will not proc nearly as much as those unhindered. For a pure farming situation, Grim Harvest (+15% treasure chance) seems viable.
War Cry: Two shouts? Man, I must be spending all my Fury on sho- oh wait, another free Shout that gives free Fury every 30 seconds. A 20% armor gain to your entire party, depending on the likely multiplicative effect of additional armor, could be quite a gain in defense and adds to the build's theme of "things hit me, but they don't hurt nearly as much as spamming Revenge heals me." I went with Hardened Wrath as rune choice, bringing the personal and party buff to +40% Armor, however Impunity may be useful in heavy magic areas and Invigorate could possibly be used in lieu of another life-leech rune like Rend (see: Bloodbath or Ravage on Rend which could both be useful in heavy mobbing situations).
Passives: We ought to have plenty of life leech and Fury to play around with, given that our only Fury Spender at all is Rend. Everything else buffs you up and gives you Fury. For Passives I went with pure Defense, using Nerves of Steel (+Armor of 100% Vit) and Tough as Nails (Armor +25%, Thorns +50%). Superstition fills out our defense, giving a physical fighter a much needed +Magic defense (20%).
General Play: Every 30 seconds, your shouts are going to give you a total of 60 free Fury. You can then put this Fury to work solely on Rend spam. If you swap out Ignore Pain for Leap Attack? Then you could be very well entering any large-scale combat at 75+ Fury. Two Shouts with their Fury generation both are better numbers-wise than taking the Unforgiving passive (1 Fury every 2s) without any heavy downtime. This is a swappable build, so if you aren't doing enough damage but taking too little damage? Drop a defense skill/passive and put in an offensive.
It's all about balance and exploiting Revenge!