He haven't showed his true power in the battlefield yet because it is not needed. They have been fighting for one year and all they did was two rasengan (did nothing really, he healed himself) and two punches. Let's not even talk what Obito have done to them, lmfao.
Since both Madara and Obito have Rikudou's power they are OP as hell, Kishi can't just let them go all out because the main character is there. How many times how Naruto been out of chakra 5? 6? We haven't heard one little wheezing froom Obito.