My barbarian has:
1000 all resist
(when it comes to resist/armor, I'm getting close to bumping up against the 80% reduction of damage mark.)
I have studied intensely on which skills to use for inferno.
I can roll act 1 inferno with no problem, and I have farmed(butcher runs) for about a week. I then used the proceeds from the AH to get myself some gear that has all resist, vitality, and strength (which yielded my info above) so I could head to act 2. I Spent about 10 mill and countless hours over the last week to achieve this. I also spent many hours hunting deals to get the most bang for my buck out of my 10 mill. Considering barbarians need all resist, str, and vit armor, good gear is obviously very very expensive. To be able to buy gear thats at all better than my new current gear, the cheapest upgrades I could get in the AH would cost 150,000,000 gold total for all new everything. No joke, and I'll get back to this. So, with this new 10 mill worth of gear, I spent countless hours playing in public games and with friends that have other classes. Just to test the viability of the barbarian.
Starting in act 2 this is basically how it goes, my friend "dude c'mon tank," me "dude I can't". I can't do anything. I get rolled so hard starting in act 2 inferno its honestly funny. I can't tank or play the roll of a DPS'er. My huge effort in upgrading my gear (great gear is about 3 times more important for Barbarians than any other class) has basically yielded next to nothing. If I were to post pictures of my gear/stats, and a video or two of my experience with act 2 inferno from just running around.. nobody would bother to roll a Barb.
Viability of the Barbarian?
What if I spent that 150,000,000?
Basically the only upgrades I can accomplish for all this gold is a 1.2 increase in protection.
The only true upgrade I could get, considering the best of the best on the AH, would be to increase my DPS. I already have a weapon that does 1000 damage base, with the added stat of +230 strength, and some vitality too among other things. I could get a little better than this though of course. Basically the only thing 150 mill would yield me is having armor that gives 200-250 strength (75 all resist 100 vit), instead of 100-150 strength (70 all resist 100 vit) So I could up my DPS from 19k to about 25k, possibly a little higher. I don't want to get this to long, so without explaining and crunching a bunch of numbers on here, I'm just going to say this isn't going to do a heck of a lot. It would allow me to carefully after dying a million times to get to the end of act 3 and act 4. And allow me to kill inferno diablo, just barely, so I could be able to make a nifty youtube video. But secretly I'd still be getting my butt owned everywhere I went in inferno act 2 and beyond. Which isn't really even to mention elite packs.
Are barbarians viable? Well yes of course in the sense they can kill inferno diablo, we've seen it on youtube. But ultimately the answer is no because as-is they will never be able to farm with any effectiveness. Or, tank for their buddies during group play in inferno act 2 and beyond. Also, its already known they can't be stacked for DPS and have any survivablity. The classes are without a doubt not balanced well. If I take my Barb that is set up pretty sweet with the numbers I have above, into a public game in act 2, other classes are winning and I'm dying, repairing, buying potions, dying, then I'm broke.
Anyways, just wanted to share my experience with Diablo 3 playing a barbarian.