Killing the Rakk Hive is story related and cannot be missed. I found the most effective and easiest way to bring down this beast is with a revolver and shooting at its 4 eyes, which will cause critical damage. The boss should die by the time you've shot out all 4 eyes. It's a slow moving boss so you can just move around it. I would not focus on anything else but shooting its eyes to end the fight as quickly as possible. This method should win you the battle in less than 5 minutes.
Happy Hunting :)