If you're using a shield and a sword instead of two swords, you're at a fundamental disadvantage. Let's say that the shield blocks 50% of all hits to you. Then it would seem that you and an oponent with two swords would be equals, right?
No.
The problem is that your enemy only needs to train two skills: Sword and armour. You, on the other hand, are burdened with a third skill to train: Shield handling. Therefore, for shield handling to be good, it needs to have an unballanced benefit given to it. Otherwise, it will be better for fighters to just pour training into the other two relevant skills.
I don't like the idea of a seperate skill for using two swords. I would imagine that such a skill is implicit in the various weapon skills. Instead, what I would like to see is that certain weapons require two hands. Claymore would be a good example of this. Really, Claymore should have speed 3.00 and slash 6.3, and it should require two hands. If 3.00 seems too fast given that broadswords are 3.00, I'll remind you that a battle axe is only 2.40 - much faster than the broadsword. Broadswords should therefore be tweaked as well.
I also don't like the idea of people being able to wield two long swords at the same time. Two sabres, definately. Even two short swords. But two long swords would tire you out pretty quickly.