I would disagree with you on this. Tsunade knows that when Naruto wins, it's because he is lucky. She is well aware of his egregious shortcomings, which include his inability to use common sense. I think her motives for making Shika take Naruto on this mission are twofold. Firstly, she sees it as an opportunity for Naruto to grow and mature, and gain more experience. Secondly, she knows Naruto's character, his strength of personality, which helped to convince her to return to Konoha. She has also seen the influence that Naruto has had on other people, bringing out the best in them by just being who he is. I think that this is what she is counting on, more than Naruto's fighting power, to bring Sasuke back.