The thing is, Kishi is focused more on larger themes than battle based logic. Obito will ultimately be defeated, not because of the power of the attack, but because of the support Naruto has --the support he could have had. And, it doesn't matter that Naruto doesn't think of them as tools (I agree, he doesn't) but again Kishi focuses on certain themes the Konoha 11 aside from Sakura (and Neji because he's dead, unless he's resurrected) + Sai will be Naruto's biggest disciples, his biggest agents, his most devoted followers. Among those 9, Shikamaru will be top dog because he's also taking the adviser/brother role that Tobirama had. Thematically, Sakura is separated from the others. Kishi gave her the spousal role when she gave the speech in which she spoke for Naruto, so now Kishi is working to separate her from the crowd.
And if you recall, last chapter we saw everyone participating in the attack against the tree --Sakura included, but the other 9 excluded. Think of who the 9 of them were, Kurama's nine tails (or Naruto's own 9 tails) perhaps?
I don't think you're nitpicking, I get your perspective and often I wish Kishi was more detail oriented than he is, but Kishi tends to focus on the themes he wants to convey, he wants to share and close certain themes and because of that I don't think he's as detail oriented as you and quite a few others are.
It's thanks to Naruto's senjutsu that this maneuver of theirs is even working which even after having received the support of Sasuke's Susanoo and nine highly amplified Rasengan spheres seems extraordinary that they could even challenge the weapon that is supposedly Hagoromo's own personal tool of creation. His power is derived from the entity that is apparently the planet incarnate and yet it's supposed to be accepted that a handful of beings with only half of a fraction of its strength, with the power of a chakra infused warrior and some senjutsu augmentation, can defeat it? I think this is where the suspension of disbelief comes into play.
Don't get me wrong. I understand completely what you're saying about the nine's intervention being important both narratively and morally. I just feel that it could have been presented in a more reasonable way. Kishi could at least have had Tobi try and use more of the abilities that he has at his disposal thanks to the Rinnegan and Jubi to try and stop them before they can attack or something. Hell, just make him look more competent visually and that would suffice a little.
I don't think that much will come from Sakura's absence besides the possible Rin parallel confirmation (if it even occurs at all since she's preoccupied with healing the Alliance in another area of the battlefield against a creature that could feasibly outlast Tobi). At least not in this fight and not to the degree that will it somehow overshadow Kishi's friendship symbolism in this chapter.
I will say that the actual fighting hasn't been all that great recently. Compared to the fights that we once saw in mid P2 (Deidara, Pain, Itachi) this doesn't look too good. To be fair though, many fans argue that the Invasion of Pain arc was the peak of Shippuden.