I don't know why a lot of people say this. When I was a 32, my Black Hammer only did 14k dmg and with Weapons of Light it did 20k. Now it does 17k base damage and 22k with WoL. And before you say it is because of ascended weapons, in Crota's end as a 34 you will be able to kill him in 2 swords even if you only go for 3 hits every time he goes down. TL;DR light level does make a difference. (Nothing earth-shattering though)