That is what Wenger says each and every time a season starts.There's still the potential for Özil to add more goals to his game (and probably to be a little more influential on how we play) as he's very capable of scoring them if he really trusted himself but for some reason it's never something he can really do over a full season.
Wenger also said a couple of words about Özil recently which confirm what you're saying:
The boss also said the Mesut Ozil could have a big role to play, as we look to reach the quarter-final for the first time since 2010.
"It’s time for him to score again," the manager said. "Maybe he will find confidence back as well, because he misses chances. He is missing the chances that don’t look unfeasible for him."
"I felt he didn't feel confident against Hull. It’s always a problem because you think he can deliver something special, but it’s true that technically he missed things [against Hull] that he is not used to."