If you remember, he was offered a contract at 150k to stay on. He may have signed that for one year to prove himself next year (due to all the points you've correctly raised) in the hope of an upgrade or a better contract at another club. Jack Bird was in a similar position.
I'd rather have Doueihi, even for depth at 150k, than someone who is unlikely to get selected if injuries hit.
I'd put it down to a salary cap decision for us and an opportunity for Douehi to show that his injuries are past him. At 150k, it doesn't matter if he plays cup all next season because it barely impacts our cap, but provides good depth. I don't mind it.