I think GW lost some good theme options when they try to equalize things and 'zerks with 1H weapons are a clear point of this for me.
When I personally play them in my Isengard army I use them 2H 100% of the time. They are raging, blood-crazed beasts. I hardly picture them slowing down in the middle of a fight to decide if they are more efficient with their big sword or if they should pull out a dagger.
Watch the scenes of them being raised on ladders to the top of the wall and see how they fight. Yeah, most of those sword swings are wide, slow arcs (that's how our Heroes slip in and kill them), but they are powerful and cut thru anyone unlucky enough to be standing there.
In the game I find that mixing several Berserkers in my force among my sword/shield Uruks more than makes up for the "weakness" while staying true to the imagery PJ gave. The standard Urks can team up with their big brothers and generally win the Fight and the Berserker is almost a guarantee kill. Match one up with an Uruk Captain for even more fun.
I'm not one for most "house rules" mostly because if you play with others you can't be sure how they'll go over, but just because the rules give you an option that you don't agree with doesn't mean you need to take advantage of it. Just because you CAN have your Berserkers fight 1H doesn't mean you ever have to.