From the 'Dual wield' help file:
Dual wield has an affect on things like shield block, parry, dodge.

How does dual wield impact those defences? I can get parry, as two weapons give you twice the opportunity to block with. I think I get shield block, i.e. if you're dual wielding, you're obviously not holding a shield.

Where does dodge fit into it? How does dodge get impacted by dual wield and what you're dual wielding?

Also, how much the type of secondary weapon impact parry vs. the primary. For example, if I hold a sword in my main hand and axe in dual wield, will my defenses be equal to axe in main and sword in dual, or is primary much more important?

Thanks.