I don't think those numbers are that much out of line with most schools.
http://sports.espn.go.com/espn/wire?section=ncf&id=7525479
And
Here is an article from 4 days ago talking about the 8 players Iowa has lost since January.
http://www.thegazette.com/subject/sports/iowas-attrition-level-set-at-nagging-20150824
Great article about Oklahoma losing players.
https://thefootballbrainiacs.com/ou-oklahoma-sooners-football-recruiting-transfer-attrition-problem
Iowa State is not Oklahoma though. They just bring in another 25 4* and 5* guys and move on. Programs like ours struggle. Paul himself has said that it's worse to bring in a guy who can't cut it than to miss on a guy.