i tend to think that being a hybrid cav is the most effective hybrid there can be. invest 6 points in riding and there you go zooming across the battlefield with a horse that does really good bump damage and backstab all the way. You dont feel like playing cav or need to save up? well you can go on foot and be as decent as any infantry out.
If you see a hybrid thrower, he has to invest those 6 pt, a decent amount of wpf and wear light armor in order to be less impact then cav on the battlefield.
Maybe cav doesnt require enough build sacrifices? is cav to easy to acces for someone who has a loose skill? Just tossing some ideas in