Don't see how when a senjutsu enhanced Rasengan did nothing to Kakashi. Itachi doesn't even need Susano'o to block that.
Well being an Edo would weaken his power, having most of his chakra absorbed by the god tree earlier wouldn't have helped and Minato didn't thrust the Rasengan into Kakashi, it was kicked at Kakashi. Itachi's body is weak, he has a disease and needed medicine to stay alive, the disease even made the MS side effects worst for Itachi, Sasuke mentioned how Susanoo made every cell in his body ache and wondered what Itachi must have felt.
always thought Minato was superior BUT, to be honest that SM was a MASSIVE ass pull U_U
Not really, Minato been Jiraiya's student since he was a genin and was always Jiraiya's favorite, Pa toad even saw both Jiraiya and Minato in Natuto during Pein arc. How would he know Minato if he didn't train him in Senjutsus? They're not summoned except to aid in SM.
This changes, literally nothing.. Sm isn't helping him with genjutsu, ask Kabuto. which is the main offensive tactic Itachi will require to go up against Minato in the first place..
It was already said that speed>Sharingan as we seen with part 1 Sasuke vs Lee, Obtio vs Minato, Sasuke vs A and Sasuke/Taka vs Bee. Doesn't matter if you can see the movements, you have to be fast enough to actually counter. So instead of trying to cars genjutsu, you'll be too busy trying to keep track of the movements. Also none of Itachi's genjutsus would work on Kabuto, he needed to use Izanami which he stated himself to not be a jutsu used in real combat (cause setting it up leaves you open as shown with the many fatal blows Kabuto did). Also Minato doesn't fit in the category to fall for the jutsu. Also the use of clones and can fuse with Ma and Pa since he had perfect SM and that's when Naruto learned all senjutsus