Lead Multiplayer Designer for Destiny and I had a little convo. He indicates that it's weapon power vs target defense. [quote]A 34 can get kills with a rare weapon easily, but a level 25 will just tickle you with the same weapon.[/quote] A 34 using a rare weapon is being severely capped at damage. You would most likely see little to no difference between the 34 and the 25 using the rare. [quote]Try using a 365 Thorn as a 34 and then try it again as a 20.[/quote] The Thorn does the same damage whether you are a 34 or a 20. As [i]explicitly [/i]confirmed in the linked conversation.