Itachi is going to spawn Amaterasu all over the ground to actively evaporate the mist; then knock out both of the Mizu Bunshins with Amaterasu coated IS..? Meanwhile, Deidara, Kisame, and the Mizu Bunshins are doing absolutely nothing? That's awfully convenient.
It takes a single handseal and a couple seconds at best to initiate the jutsu and spew out an entire lake worth of water [
You must be registered for see links
]. The Mizu Bunshins being equipped with Samehada clones (and all it's abilities) will also be able to sense out the oppositions location. There is absolutely no need to surface anywhere remotely close to Sasori and Itachi, as the AoE of this jutsu stretches out for quite a far distance... nevermind two of them being combined. Then we have Deidara and Kisame who can easily stop any efforts at knocking out the bunshins, by immediately forcing Itachi and Sasori on the defensive. Bakusui Shōha will completely engulf the Amaterasu flames, and result into even more mist. This of course, wouldn't be a problem, as Amaterasu isn't by any means evaporating an entire lake worth of water at any noteable pace. In fact, this isn't even a slight issue when the Mizu Bunshins will simply absorb the Amaterasu with Samehada. All the while, the real Kisame is still actively emitting mist, with his tailed beast level chakra reserves. All in all, this is wasted effort and chakra on Itachi's part.
Deidara doesn't need to see his Jutsu's location in the mist. It has been demonstrated multiple times in the manga, where ninja are capable of gauging an accurate amount of distance with vision alone [
You must be registered for see links
]-[
You must be registered for see links
]-[
You must be registered for see links
]. Deidara's clay bombs are remotely controlled by him, so if Kisame reveals the oppositions location, it shouldn't be hard for Deidara to accurately direct his bombs within a close proximity. Alternatively, Kisame can simply guide Deidara's clay bombs
You must be registered for see links
. Barring C3, none of Deidara's bombs are strong enough to completely disperse the entirity of Kisame's mist. You have a good point, in regards to C4, but a simple solution to that is: Kisame will simply
You must be registered for see links
his chakra into Deidara, which would be used into forming the C4 nano-bombs. It will go completley invisible to Itachi's sharingan. Poison enters the blood-stream, and attacks the cells. Not possible with a Mizu Bunshin (assuming this is even a factor). Not that I'm even endorsing the notion of Totsuka being a viable counter, but Itachi wouldn't see the GSB due to the Hidden Mist. Why doesn't Totsuka just conveniently seal the Mist as well?
You forgot to address a Kisame enhanced C3 bomb as well, but I suppose it just get's sealed into genjutsu along with the rest of Kisame and Deidara's arsenal.
Yamata no Jutsu is a transformation technique, and thus a
physically linked extension to Orochimaru's real body. Not exactly comparable to elemental ninjutsu. Itachi had to wait until Orochimaru revealed himself, to actually pierce his soul and seal him away. If Totsuka was capable of sealing all ninjutsu, then he should of done so against Hydra, rather then waiting around for Orochimaru to surface. Also, if it was capable of doing so, then why was Orochimaru's chakra (in the form of smaller snakes) able to escape being sealed? Are we thus implying that ones soul is also capable of escaping after being peirced as well? Surely not. The mechanics behind Totsuka is being capable of sealing ones soul, along with whatever it is physically linked or attached to (ET body and Hydra), after being pierced.
@ the colored text, that is exactly my point. Elemental ninjutsu has zero correlation. It's not directly attached to the hosts soul. Shiki Fujin and everything else is irrelevant.