The rankings that the staff had mostly came from the season's run in beta testing. The top ones aren't necessarily the best, just those that had the most success.
I have a system I use for scouting potential staff and drivers. It has nothing to do with scout reports.
Scouting reports are only as accurate as the scout, which is why I do multiple scoutings, and have multiple scouts (yes you can have more than 1 scout, and they will all do reports).
I don't want to give away all my secrets, because then you'll all beat me
I would say your scout isn't very good. If you want more accurate scouting reports, do multiple reports on the staff member. Also, try and get a few scouts. Overall I feel they should average each other out and you're more likely to get results closer to their actual skills.