1. The Sharingan didn't actually keep up with the Raikage; he was never once hit by Amaterasu. He was injured by Sasuke manipulating black flames through the blaze release.1.Who cares if they are fast Sharingan can keep up with Raikage.
2. I already anwsered that.
3. When has susano'o really been disabled throughout the manga?
4. They never fought a sharingan or a Ms user for that matter with that much exp. So I don't know where you got that from. What you think Gai taught them how? No. Gai for all we know is the most successful fighter against a sharingan user.
2. The Mangekyou Sharingan has repeatedly demonstrated that continued use greatly tires the user, and even damages their eyesight. Even with the Eternal Mangekyou Sharingan, their eyesight will never die, the techniques of the Mangekyou still take massive amounts of chakra, and Sasuke wouldn't be able to maintain them for a great amount of time. The Mangekyou Sharingan is not limitless.
3. Susano'o has been broken through multiple times. The Mizukage actually damaged Sasuke while Susano'o was still active. And Oonoki and the Raikage punched a hole through it...also, the point is that Neji can PREVENT Susano'o by closing Sasuke's chakra flow, not defeat it once it's active.
4. If you think Guy didn't share how to fight the Sharingan with Neji and Lee during their training, and ESPECIALLY when Sasuke was declared an S-class missing-nin, you would be wrong. Especially Lee, I believe would be able to successfully fight.