Then why doesn't Itachi do that with Kisame or even Sasori? In your opinion Itachi + anyone = Perfect team because itachi is so skilled that he could do something like that. But you never see anyone under a Genjutsu ACTUALLY being controlled by the caster. That leads me to believe that it's not possible.
Genjutsu alters the signals the body sends to the brain not the opposite way around. Its hard to understand if you don't get it right away BUT you eyes don't actually "SEE" things, they just take the image and translate it into a signal that the brain can comprehend. You don't actually "HEAR" things with your ears it just takes the signals of sound and changes it into something the brain can comprehend.
What genjutsu does is it changes those signals of the 5 senses, to alter them to the way they want. It'd take a lot of effort to control someone through these sorts of aspects.
Next of all, why have ONE person do the amount of work for 2 people? When both of them are PERFECTLY capable to do the same amount of work themselves?
Lastly, Hidan + Kakuzu were a perfect team regardless of what you say. Them TOGETHER were UNBEATABLE. That is why Shikimaru split them up. He figured that out. If Hidan + Kakuzu didn't get split up then they WOULDN'T have gotten beat. Regardless of who was there.
strongly disagree. here is why.
first and foremost, controlling one is entirely possible. orochimaru did it with the 1st and 2nd hokages vs sarutobi, nagato did it with dead corpses, danzou did it with the samurai guy at the summit, the list goes on...
secondly, if itachi were capable of it then yeah, itachi + anyone, or any sharingan user of itachi's level + anyone would be the best team.
thirdly, obviously whatever one sees and hears in an illusion is nothing but an illusion. however, your argument precludes the fact that MS genjutsu may be slightly different, in that it might not only be caused by variations of the five senses.
furthermore, why have one idiot do part of the work? think of the team as a watch. it'll only properly work so long as all the gears mesh and work in unison. should a wrench be thrown in, everything stalls. same principle applies to a team. a team is only as strong as its weakest link, aka hidan. why allow an idiot to tave part in the decision-making? thats just counter-productive.
and lastly, itachi need not cast a genjutsu on kisame because he KNOWS hes already really strong. he KNOWS kisame wont act rashly and get himself killed or in a situation which requires his teammate's aid. and itachi KNOWS kisame better than anyone; if he were able to cast mind-controlling jutsus and still left kisame with his own mind, then clearly he had faith in kisame's abilities.
edit : and i forgot to mention, shikamaru did not seperate them because that was the only way of defeating them. as smart as he was, he probably deduced it was the easiest or safest route to take. but that wasnt why he did it. he seperated hidan so he could take care of him himself, for he took the life of his master. THATS why he seperated them. he wanted to avenge asuma with his own hands.