Before Toughness is subtracted and the location of the attack is subtracted from armor, each creature or npc that you fight has a armor rating. With any attack, especially dual strike, swift attack or lightning attack, yes there maybe one or more attacks but according to the rules, first you have to succeed on the ballistic skill or weapon skill test, find hit location by reversing rolled characterisitic number and for each roll you succeed in beating the target number by rolling even with the number OR under it, you get individual damage rolls per number attacks the talent gives. So yes subtract armor and then toughness then your left with total damage. If the damage is equal to or x2 the toughness modifier bonus then the creature is lightly wounded. If the creature is any more damaged than x2 it's wounds then the creature is heavily wounded. Please note that critical damage is rolled after the wounds drop to below 0 wounds and then you would check the critical injury chart per type of damage from weapon.IE rending, energy impact etc…..