It's going to depend on who you are riding with. I ride with a large club and our groups are completely random in their pacelining/drafting. In other words, nothing is expected of anyone, (except for safety concerns). The strongest few riders will take the front and hammer and everyone else will scramble to stay on. When the hills come many of us will get spit out the back.
Sometimes a faster racer/beast will pull most of the ride and most times there are many riders who sit in every inch and never feel the wind.
A few weeks back I did one of these rides where 2 racers pulled most of the 65 miles and the group went from 40+ riders down to 8 at the end. I felt like I had been sprinting for hours (probably because I had been).