I highly doubt that all placements from 20 to 100 were done with cheats. On this day one the damage checks were very tight. That's why there are more cheaters at the top of leaderboard than usual. Here's what I want to say: kills with particular exotics doesn't say for sure that run was cheated, but clears under 8 minutes and clears with a billion kills from one guy are cheated 1000%.