If I understand it right... If you use both weapons at the same time they do more damage?
That is a problem?

Yeah so in 99% of games movies and RL people usually swing the swords not at the same time but more of a timed actions like swing swing swing swing well sounded better my head hard to explain but you sort time the swings in and out so you usually have 1 weapon going or at the target. In Skyrim it's like a special head slicing attack that you are suppose to do EVERY attack for optimal damage of dual hand weapons.
Meaning you stand there spamming both weapons same time with the worst animation possible to do good damage.