As a GM I'd say that you can apply half to each attack. I'm not sure that rules as written though.
Apologies for cross posting this, but I thought of this as an alternative for how to handle two weapon fighting and want to float it to see if other people like it. So since this is a dual wielding thread, putting this over here too.
Dual Wielder
You are trained in using a weapon in either hand.
Effect: when you are using a finesse weapon in either hand, or a dagger or hand axe in the off-hand, and you hit, you may roll the damage dice for both weapons and use whichever one is greater.
You'd lose the ability to attack two targets (I'd design some higher level feat for that), and you wouldn't do more damage than with one weapon, but your average would be a little higher.
Upper level feats: some kind of cleave that allows you to attack more than one opponent with your two weapons, and eventually the ability to use two one-handed, non-finessable weapons.