So I was playing earlier today when I was evolving up my guns ( I run only with exotic and legendary weapons) when I realized my legendary scout rifle (just barely got it) was doing a a lot more damage851 crit then my exotic ( meta multi tool) which was completely upgrade 801 crit.... basically the only difference with the two are upgrade status and the part that acutely measures the damage is bum bum bum buuuuum, impacted. ...that is the only thing in your weapon statistics that provide damage rating on your weapons. So in a nut shell rarity and upgrades don't matter its all in the impacted rating. ... hope this helps because it pisses me off