Yeah, we pretty much run on whoever shows up for the meetings. We have an Administrative, Communications, Project Management, and Finance officer on the team (elected positions, chosen after Nationals of that year). We're lucky if we can get a group of 10 to 12 dedicated students, and even then it's tough to get everything together. We usually have one person skilled in one precise area, or a group of people, so things generally run in that area by what they say.
In our school, robotics is an afterschool club. Only after winning a regional does our school even start to acknowledge our existence (for more bragging rights...). Our school also has a robotics class this year, but it won't be a class next year and this year they wanted nothing to do with us. Instead, they built a blimp... using our tools and our room. Unfortunately, the class is taught by the same teacher sponsor of the club (even though he doesn't do anything for us anyway), so it's allowed.
I wish we had to take applications... it's easier to cut some people than waiting for more than 4 people to show up on a build season day.