Dual Wield is actually pretty amazing, but there are two things you should know.
First, there's a serious penalty for off-hand damage when you first start the game, but as you invest points in the skill the penalty lessens considerably and eventually you even get bonus damage!
Second, and I'm afraid this is not made very clear in the game, is that the damage you do is actually twice
the number that is shown, because it shows the average amount of damage per hit, but of course you make two hits per attack: one with each weapon. So if it says you're doing, say, 10-25 damage, that means you do 10-25 damage with each weapon, which means you'll actually be doing 20-50 damage.
Bit complicated, I know, but in the end Dual Wield is a very good way to go (though there's nothing wrong with two-handers of course).