Dozer, i think your question is good, and your theory is logical. Problem is...it takes far too long to prove. I hunted bps for 6 months of this game (along with all the other stuff to do) and i never found Avengers. Hunting solo, I have found assault rifles, flamers and miniguns but not often. I find what all the other guys find usually: alloys, basic pistols, small ammo, and caps from 1 to 600. Leather armor and jackets, radios etc.
My guy is Luck 10, Big Guns. I found CA bp 2-3 times but never found CH, p90, or Improved Flamer bps. What we would need to do is compare notes over time using different builds and tracking results somewhere so it's not just a guess when we're done. I also find tons of FCC but that may be a Luck thing.
Also it would be cool to group-hunt lockers and see if maybe the results are any different. This is one of the mysteries in this game so we're not likely to get a dev to explain it outright.