Patch 1.0.3 has drastically changed the game, to the point that most strategies that have been developed for barbarian are no longer optimal. The focus now is on DPS and clearing speed, not survivability.
First, I'll talk about the optimal farming strategy, and then the builds you can use to complete them. The Nephalem Valor Buff change means that bosses will drop less loot, while elite packs after the 5th will drop a lot more. This rewards a farming strategy that kills as many elite packs as possible in a single run. Therefore I recommend that your farming run consist of entire act farms, maximizing the proportion of elites that are killed with 5 stacks of valor.
Act 4 farming is bad because it is so short. There are only about 10 elite packs in the entire act so only a few will be killed after the 5th stack. Whimsyshire is also inefficient, first because it only has a few elite packs and also because of the magic find change; it does not affect clouds anymore (didn't get a single blue when I tried it.)
Therefore the best farming routes are full clears of acts 1, 2, or 3. Since a full clear involves killing about 30 elite packs and several bosses, it could take up to 2 hours to complete. In the interest of efficiency I recommend you farm the highest act you can while using a dps strategy. The drop rate change means that farming act 1 in 90 minutes using a dps strategy will be more rewarding than clearing act 2 in 3 hours using a tanking strategy. The most efficient farm in the game will be the fastest completion of act 3.
Survivability requirements have dropped drastically. I was able to drop my EHP in half while tripling my dps and still clear act 3 without too many issues. Currently I clear act 3 in about 2 hours, killing 30 or so elite packs and all 4 bosses, which translates to about 4 full backpacks of loot and 50-60 rares. My stats are 7k armor, 700 all resists, 60k hp, and 40k dps, further boosted by brawler and berserker rage.
I was able to get such a high DPS by stacking as much Crit hit chance and crit hit damage as I could. Currently at 46% and 289%, respectively!
Arcane enchanted seems to be the most deadly affix right now, especially when paired with affixes that constrain your movement.
I'll also share the build I use but first I want to talk about build diversity. It is no longer necessary to use a cookie cutter tank build, but you'll probably want Wrath of the Berserker with the Insanity rune and Revenge with Provocation, as they are our most powerful skills. You can satisfy the meager defensive requirements in any number of ways, whether using passives, high EHP gear, War Cry, Ignore Pain, or even using a shield. Yes, sword and board is no longer necessary, 2h and DW are just as viable!
I currently use:
Wrath of the Berserker(Insanity): Once you are over 30k dps you can kill act 3 packs within the 15s duration, which makes this skill amazing.
Revenge(Provocation): Very strong and reliable skill, gives you both sustain and strong aoe damage. Practically a requirement unless you are using a whirlwind or ranged build.
Ignore Pain(Ignorance is Bliss): I chose the lifesteal rune, even though it is nerfed in inferno, because my high dps gives good returns. When I pop Wrath of the berserker I do about 500k aoe dps, which means 4% lifesteal gives me back 20k hps! That's better than an extra 2 seconds duration.
Leap (Iron Impact): One mobility skill is a good idea, and leap doubles as a defensive cooldown. I also like that I can take shortcuts by leaping over gaps and walls.
Frenzy(Sidearm): Still the best single target dps skill for this build. Also provides some bonus aoe damage! Excellent for small packs and boss fights.
War Cry(Impunity): Still a great defensive option, I chose to keep it and replace my defensive passives because war cry is just so good
Passives:
Berserker Rage: I don't have any fury spenders so this is an easy 25% more damage.
Ruthlessness: Ties in well with the crit hit chance/damage build.
Brawler: Being surrounded by enemies is where I want to be. Massive 30% increase, but stops working as you kill a lot of stuff.
I want to replace Brawler with Weapons Master (Axe/Mace) because of the crit strategy and also because Brawler is useless against ranged elites. Just gotta find the right weapon!
Check out my stream for a demonstration or to ask questions
www.twitch.tv/zrave
Also, I'll be uploading new guides for 1.0.3 content to my youtube channel!
www.youtube.com/zraveX
TL;DR: Blow stuff up