Anyway, Sakura's development is a bit strange. First, during the first arc after the time-skip, I was inclined to believe she had developped even more than Naruto. Then, for six years - FREAKING SIX YEARS, DAMNIT -, we saw no progress at all. Even when Pain attacked, or when she went after Sasuke, she looked like a true dropout. It's true she looks like a Tsunade-clone, but to be honest: I didn't really expect her to become stronger than Shizune, let alone as strong as Tsunade. And now, she as a contract with one of the best animals there are, is much stronger than expected, and she has a chakra-seal with a huge potential. She may still be weaker than Naruto or Sasuke, but it's not really fair to compare her with a Jinchuuriki who fully cooperates with the strongest beast or with an Uchiha who got the EMS handed over by his brother. However, healing techniques are extremely important in battle, and the rest of team 7 will depend on it.
And I really hope we will learn how the sannin-apprentices surpass their masters (before they even turn 18 ;-) )