maybe more like:
4 bot on
1 person joins, 1 bot drops
1 person joins, 1 bot drops
1 person joins, 1 bot drops
1 person joins, 1 bot drops
I'm not sure how it is with TF2, but it used to be with CS that people wouldn't join an empty server. But on the other hand, people who joined a server thinking it had people in it would be annoyed when they joined and found out the majority of the "players" was bots.