Sounds like you stumbled across some engram farmers, they're usually harmless players who sometimes don't like it if you inadvertently stand too close to certain spawns, standing in them can pause the enemies from spawning. The most popular spot is a cave where the hive are at the cosmodrome. Next time go ahead and join in for half an hour or so and harvest some awesome gear, just stand where they stand shoot what they shoot and run in to claim your stuff together.