I agree with people who think that Sasuke is using a genjutsu like tsukuyomi. First of all, it's a lot like when Itachi used it on Sasuke and it showed Itachi taking Sasuke's eyes out. I mean Itachi didn't really throw Sasuke into an alternate dimension type thing. Also, the illusion was one that Sasuke was very afraid of. In addition, Sasuke wasn't able to get out of the illusion for awhile. This is all kind of the same with the current battle. Itachi was a person that Danzo probably was afraid of. Sasuke using a genjutsu to bring him out would be a good tactic against Danzo.
On a different point, I don't see why Danzo would be trying to wear Sasuke down. Madara's not going to let Sasuke die yet, so if Sasuke gets into danger, Madara will either save him by taking him away or fighting Danzo, and by that point, Danzo will probably also be tired so Madara will have the advantage.
Also, I'd just like to say that Sasuke is a bad fighter. I mean he has a lot of great abilities, but to use them all right away isn't really smart. I think he needs to become a more experienced fighter. Danzo has a lot more experience in fighting so I think he has an advantage. Sasuke seems to just use all of his best abilities right away, unless he has something even more amazing waiting.
Finally, I kinda miss Sasuke's fire and electricity abilities. His fireball technique was my favorite