Curry has given you a good advice to increase your DPS.

I would like to give you a very different advice.
Just another option for you.
Move away your shield.
Sell it and get another good DPS weapon with 950+ LOH.
With 2 weapons, you have about 1900LOH.
Then, try to get another 400 LOH from your amulet and rings.

You will go dual wield with this build.
You will have at least 20K DPS. That is good enough for A3/A4 (especially after the patch & REND).
You will have 2200++ LOH too.
With such LOH + the skill REND, you can whack like a boss in A3/A4. 

I did the same and I could just stand there and whack without kiting.
I got killed 1-2 times during the game (A3/A4) if there are 3-4 arcanes + fire + poison hit me simultaneously.

P/S Let's not forget, with LOH build, you can opt for WW-Tornado (IMO, I think it is the best build for barb, offensively and defensively)

P/S You have problem because you have half-baked LOH. 950 LOH doesn't give you enough impact.
Double your current LOH + another 400 LOH (you need at least 2200 LOH) to be a boss again. 

lifesteal and LOH are different.

Why need to block?
I'm not saying you can't use shield & block.
If you need shield, at least, you need to increase DPS.

Basically we see 2 types of Barbs that do well in A3/A4.
Barbs with high DPS (with or without shield). With REND, they are like boss now.
Barbs with WW-Tornado, they kill monsters in bulk like boss.
Both builds are offensive type.

Barbs don't go defense anymore. 

P/S I give you another option, Barb with high LOH (you need at least 2200LOH + 20K DPS).

Nice dual-wielding build there mothangel. For those who prefer 1H+SS build, here is mine... will usually slot in 18% life gem in my helm but prefer the bonus exp for Paragon leveling now.
http://us.battle.net/d3/en/profile/Barbabr...19/hero/2033556