The barbarian sucks giant balls at low levels. It's clunky, it's slower than everything else due to being melee-only, fury generators don't generate enough fury or do enough damage, on and on...

Once you hit level 50+, the barbarian starts to turn into A BARBARIAN. You're not fury-starved anymore, you have enough HP to take hits while you round up enemies and cleave them down (I'm playing rend + maelstrom), you can blast through packs just as fast as other classes, and it's generally a WAY better feeling class to play.