Berserkers are Warriors on steroids. They take the strengths of whacking stuff to death and multiply them by three, sacrificing speed, magic and luck in the process. They don't need those stats though. Most Berserkers dual-wield weapons and forgo armour. Why bother when your job is to get in, demolish, and get out? There's no use slowing yourself down with extra fabric and metal when your dexterity is already horrible.
If you're aiming to maim, a good portion of your army should probably consist of Berserkers. Assign some Healers to them and bam. Unstoppable by anything except for a decent Mage or two. Applying a little restraint to them so they aren't essentially a group of kids let loose on a playground will help prevent them from dying quickly - as such, Knights or Defenders are often assigned to lead the group effort. Of course, not all Berserkers are bloodlust-y Viking warriors, so a well-tempered, good-mannered Berserker is entirely capable of being a General or Captain.
These guys don't just open pickle jars, these guys smash pickle jars. They are pretty damn strong compared to the average Freelancer or Mage. Berserkers make good farmers or miners or mercenaries; anything that lets them use their strength to their advantage. Many Berserkers end up as competitive athletes in what would be considered 'field' events, since they can't really run fast. Of course, RPGverse doesn't have the sophistication of the Coliseum or the Olympics, so they're more like the rival dad who beats you in backyard cricket every time your families play.