lvl 38 barbarian here. normal just played with 2 x 1handers, then a 2hander = faceroll... now in nitemare it aint so easy, so off to the AH I went, found a sick 1 hander and a shield with 450 defenece, and its back to stomping all and sundry. only thing that is a bit of a bastard are arcane packs, and poison >.< using the enchantress on single player. sitting with about 1.3k dps
http://d3db.com/tool/calculator/barbarian/21709 is my build. a few of the things I will change once it gets harder, but for now, its pure pwnage
I cannot stress enough, go spend time in the AH, and I mean go spend an hour or 2. make use of the option where you specify what stats you want on your gear, even the minimum amount. click the buyout bar at the top of the list of auctions. you WILL eventually find some amazing deals. trust me on this one

you just need to have some patience. also, look at time remaining for the auction, this isnt wow, on diablo it shows all the way to less than a minute left. found, bid, won, and lost some brilliant deals that way