I presume when this refers to 'Duck', it means 'Dodge'?
Not sure how this can work in practice - e.g. you've used both actions in a round and have two ranks in this, so two free dodges. After the first dodge you're prone, so how can you possibly dodge again? Even if you start using them before your actions - you'd basically have to expend all your actions getting up. Until you've taken Level 2 of Steady Feet, this isn't really useful at all. I guess it's intended to be the equivalent of the Defender talent, but it doesn't make as much sense to me.