Barbs are fine they're just extremely luck based unlike most classes with sure fire stuns and CC ability.
If knockdown wasn't so ass tier they'd be fine.
As for defense, out of a duel a scripting Barb has no excuse to die after the spark nerf patch. Granted it will be hard to kill and be killed under the current circumstances, but they are truly fine at the moment once you reach a certain gear threshold.
You could make the argument that other classes have much more defensive ability with lower HP pools, but that is an argument that will never be won, and I'm tired of trying to fight a battle that can't be won.
If you're dissatisfied with barbs as they are, roll a different class. I only play Barb because it's one of the only classes I don't get bored of after 2 seconds