Pack riding is koo koo crazy. I tried a group road ride once and made a maneuver to avoid a crack in the road and took out my friends front wheel. Boom he went and I never did a group road ride again. Riding bikes is supposed to be fun.
I was in a pack of 20 or so people cruising at a good 30+ MPH, double pace line, when a deer came running out of the woods. Some dude in the back saw it and called it out. The pack split and let the deer pass through. No one went down but I suspect a lot of shorts were soiled. This started out as a much bigger group and a few of us decided to put the hammer down to filter out the gomers. I was riding well above my abilities but it was worth it. It would have been a blood bath in that larger group.
The only time I ever went down was on a solo ride when I wasn't paying attention and hit a giant pot hole.