I was using my Sparrow to blow past the mobs on Devil's Lair up to the first darkness zone [i]well before[/i] the loot cave was nerfed. I see no purpose in killing level 8 or 9 Fallen and Hive that other folks are killing for patrol missions. Sure, there's a chance that they could drop engrams but that seems to defeat your claim that the people speed running are ex-loot cavers, since people who want to engram farm would likely want to kill everything on the screen.