Spoke at some length with a wizi imm who said that I should post, but not expect a quick resolution, so...

Even though one is spec'd in daggers, you can't dual wield the same dagger in various circumstances. The best example is the leaf-bladed dagger. It is 9lbs, 15oz. When you try to dual wield them, they just keep switching place as primary, so you end up wielding only one and having no dual wield at all.

Moreover, when you wield a fist of lightning, which is 14lbs, 15oz, you still can't dual the leaf-bladed dagger, even though it is less than 10lbs.

It kind of screws up several things, particularly what you can dual wield, trying to re-wield things after being disarmed, etc.

If you want logs, I can post for you.