Build here: http://us.battle.net/d3/en/calculator/barbarian#WTRVkP!VgS!acbccZ
this build is what i used after i start farm act 2 at ease so i can speed things up, if you still in the process, change some defense passive and replace earthquake with furious charge, makes your life easier.
My stats: 1100 str, 900ish vit, 700 resist 8500 armor 11k damage after buff.
Another thing, to me act2 seems to be a bad choice for farm since 1, the drop level looks almost identical to drop in act1, bosses often give like lv 50-59 rares and I havent found anything amazing during like one week's farming there( I get 2 really nice rare and still use them from act1). 2 a lot mobs are super annoying even after u are familiar with them, like those flying bug shooting stuff to you or those tomb guardian shoot different elements to you nonstop. So if you feel the same way, back to act1 maybe a better bet, Idk, that's up to you tho.
Farming spot: due the the second reason above, I choose to start at kull( or whatever his name is)'s home, mission black soul stone last step( cant check for names for server's down). There are three dungeons, I usually leave the realm of shadow at last since for me the loots are slightly better. Difficulty wise, realm of shadow is actually the easiest for dont have that much tomb guardians. So if you have trouble in the other two, skip them and go to this one.
Usually you can get 5-10 rares here which is enough for the 5 stacks.
Some tips for tough elites: tomb guardians are always tough, they are ranged and do insane damage with only their normal attack. Engage them only when ingore pain's up and you always want to pull them back to your check point just in case. Try to nuke one down with wrath, use charge to get in/ out of position if u use that.
Stone giant: these can be hard, they hit for like 9000, but that can be dodged. Try to get to the side or back of those giant instead of getting away, you will be surprised.
Those ghosts who can fly: dont chase if one of those getting away, stay at a spot and wait them, they are impossible to catch.
For kull, he should be easy, just in case, kill the giants first and pop ingnore pain when he calls stone on you. Be away of the tornado.
After kull you want to get back and sell all those loots and get bial?or whatever the lord of lie down.
Demons on the way hit really hard, dont hesitate if you feel potion or ingore pain is needed. Before the door of him there will always be a pack of demon wiz, that should be the easiest rares in the entire act2, they will just standing there use the blue circle skill and rarely use any of their special abilities..Just enjoy.
For boss, a lot ppl find it tough, I will just share what I do with him.
For my current build, I will pop wrath and earthquake the second he appears and get him down before he can even teleport away. But if you cant do that, which probably is due to your heavy defensive gear/build, you will like to save these two skills to phase 3 for less bomb he may drop on you. In phaze 3 what I suggest to do is standing at the top right corner below the two stairs on the map, here u can avoid his acid breath or whatever he shoots out from his mouth(> <), and it yields a good start point for you to dodge the bomb thing. Based on my experience, when he start to bomb, you want to run to the left and you always want to run on the edge, dont panic, it's not too hard to dodge after a while. Then what left is just pop wrath and kill him over time. Give him a painful death!
If you are using the build with furious charge, it will be actually easier but slower, use charge as a dodge skill to aviod his " hammer hand" and so you can save heath globes for other use.
That's basically it, enjoy your all mighty barb!
PS, gearwise, Mara's Kaleidoscope is an amazing piece to get. Like 10 times better than justice lantern especially when lanterns are no longer 400k.