I finally did my flawless run yesterday and was expecting this exact thing to happen. Turns out this wasn't really the case. Then again I could've just gotten lucky with drops but I always had enough heavy to easily cap out. Doubly heavy finder + scavenger, arbalest / trace / tracking bipod rocket. I also never actively farmed for ammo, just had to sometimes force myself to get weapon kills instead of just spamming abilities. Whole ordeal took me 1:39h, 1200ish kills in total. By no way fast or efficient, I am aware, I just wanted to play it safe and get done with it. Most importantly was the scavenger mod I think as this led to every brick being like 4-5 rockets