Give it time. It is really a numbers game for Simon/Griffin. It doesn't mean they are busts just that that Lea is getting his best 20 guys on the field depending on the situation and they haven't cracked that group yet.
To date, the top 6 dbs have been Pride, Crawford, Bracy, Hamilton, Eliot and Gilman. It isn't a "miss" when you can't crack that group. And it is rare when you need more than 6 dbs. And I think that Griffin is going to end up as a safety next year which is probably where he be probably belongs. That said, if he isn't playing a lot against BG, then there may be an issue.
Same thing is basically true about Simon. He is outside the top 6 at LB (including Rover) and Lea often uses Jones/Hayes if he wants to go big instead of using a lb.