There is no such thing as light advantage in destiny. Only disadvantage. As long as you are over the light level of your opponent, you are doing the maximum damage dictated by your weapons attack value. It's why you shoot level 2 enemies on the cosmodrome with 300 attack power weapons and only do a few hundred damage. Just try it out yourself. Load up the raid. The enemies are 280 light. Shoot them and see how much damage you do as a 330+ then put some blue gear on and use the same weapons. As long as you are over 280 light you will do the exact same amount of damage.