I'm playing a barbarian on hard difficulty. He's level 8 at the moment and has done about 34k damage with Aloth 2nd at 20k. Though to be fair Aloth spends a lot of time in fights casting debuffs and crowd control spells. Anyway I have him using a pike primarily, but switching to great sword for pierce resistant enemies. Accuracy is everything to a barbarian especially with carnage having a -10 penalty. So WF: Soldier and the accurate carnage ability go a long way to making those carnage attacks hit and when they do it tends to be for 10-20 damage.
Now his defense sucks true, but between Eder and Pallegina tanking the enemy it's not often that he gets into trouble and when he does savage defiance can just about always heal him through it. As far as one stands alone goes most people seemed to use it when it was bugged and doing +20 damage rather than the +20% it does now having been fixed. I don't and won't take it as I would hate to put my barbarian in a position where he's tanking. Don't use blooded either as I don't want him below 50% endurance ever and that rarely happens anyway.
I don't know if this helps you much any. Can say I very much enjoy playing him and he does great dps. A fighter or paladin spec'd for damage might out do him on a single target, but add in carnage and it's no contest.