When dual wielding...

do defences like parry and dodge come formt he defences of the main weapon or the offhand?

Parry comes from your defenses of your main weapon. Dual parry comes from your dual wielded weapon. Dodge is based off of your dex, -ac, and even size (I believe).

Parry comes from your defenses of your main weapon. Dual parry comes from your dual wielded weapon.

Indeed.

Unless one is a blademaster.

Thanks