This is a AOE Tanking build. Not meant for bosses.
Take in mind I'm a lvl 42 and currently on act 3 NMhttp://us.battle.net/d3/en/calculator/barbarian#bcRVkT!bdX!ZZbabb
Think of this spec as a Blood DK, or a Prot Pally spec from wow.
Revenge with the right amount of mobs can heal you big time! On top of that you get additional ticks from your Rend. and I also have Inspiring Presence which will tick around 150-200.
You will have so much self healing its stupid. I also put in some medigation into this build with ignore pain. I like to use cleave because with rend up it will generate a lot of fury.
When pulling a group of mobs, I always prioritize Revenge over anything else. So with that said I start out with: Cleave>Rend>(Revenge if it procs)> Cleave>Cleave>Rend refresh.
Always have Battle Cry up the tick is 100-200 and increases your health.
For elites with adds I will Cleave>Rend>Earthquake>Cleave>Rend *Revenge if procs.
Using this technique I never die. I mean.. Never!