Same, I still remember the day it happened. Oryx challenge, 16 blights, lag, death screen, four guardians, four blights detonated.
Guardian 1: Man F*** this, I'm done guys. See ya.
Me: (sarcastically) Nooooooo!
Guardian 1 is Offline.
Guardian 2: Oh dang! laughs uncomfortably. oh s***.
Guardian 3: *silently leaves group and goes offline.
Guardian 4: See you guys, I'm going to play ESO.
Guardian 2: Asks me and Guardian 5; we're still friends right?
Guardian 5: ......
Me: Yeah, yeah of course man. It's cool.
Guardian 5: ......
Guardian 2: Alright man, see you guys.
Me: Yeah see you later man.
Guardian 5: ...... Has left the group.
Next day!
Me: looks at Facebook raid group, 1,2,3,4,5 has left the group. :O *leaves as well*.
I stayed until the whole Matchmaking debacle. If Bungie's own employees didn't know they implemented skill based matchmaking, I can't trust anything they say.