agree, this week alone everyone in my clan (including me) got their 2nd gjallahorn amoung other exotics. I would rather believe that it looks at what you've gotten and eventually gives you what your missing, but I know that's full of holes cause since I bought two IB a few weeks back I got a 3rd and then two more. I've scraped at least 4 suros' as well. In the end if you play enough you create more chances to get what you want.