Shikamaru's plot role is the guy who leads Naruto to become the leader. He has to be the guy who can actually move the main character by his words, mind and experience. And as such, Shikamaru gains certain experiences before Naruto. The chuunin status, first mission failure, death of his teacher, execution of Sasuke and such. All these experiences are needed so that he can actually give Naruto the advise, or the support he needs (ex. Jiraiya's death).
Meh, I could have explained it better but I'm drunk and tired. Take it as you will.
Heh, you seem lucid enough to me.
Anyways, regarding Shikamaru. I agree very much. But honestly, 615 would've been the perfect opportunity to showcase that role of Shikamaru. Even now, I still puke at how forced the chapter was. That moment should've been Shikamaru's moment. That's what your right hand man does, picking you up when you're down.