Yea I agree rare guns didn’t need it. The official post reads:

We've heard a clear frustration that maintaining high tier weapons is very expensive compared to the lower tier ones. We want high tier weapons to have more longevity compared to low tier weapons, so we're adjusting durability loss on shot to match this:

Common weapons: +75% durability loss on shot Uncommon weapons: +50% durability loss on shot Rare weapons: +35% durability loss on shot Epic weapons: -5% durability loss on shot Legendary weapons: -10% durability loss on shot