Nope, story missions. Happened in Old Russia and on the Moon missions. I have it set to Public so that other people around my level can join me and we can work through missions together...but it's constantly level 30's joining and destroying everything...then some Public Event will start and they will destroy it as well.
Could be folks waiting around for public events?
I was finding that, at least on the Cosmodrome, there are so many public events that you can actually grind for Vanguard marks faster doing them than the hardest Strike playlist. Obvious exception being for 1337 $p33runners.
Speaking of which, you folks keep like Dgaf "personal best" speedruns for missions/strikes/raids? I'd love to know how hilariously fast some have been completed now.
EDIT: TOP POST!