Tobi, Zetsu clones, shinobi's reincarnated by Kabuto and Madara are taking part in the battle. But Tobi had Sasuke in a hideout under the control of Zetsu to get recovered from eye transplant surgery . Why didn't he bring to the war after he gets cured, while Sasuke had a revenge against Konoha?
It is like you said, he had Sasuke under the supervision of Zetsu, recover from the eye transplant.
Read if you are uptodate with the manga
Right after Sasuke was fit to join the fight he set out for the battlefield. On his way he met Itachi and things changed there.
Sasuke along with Itachi took down Kabuto, and then Orochimaru appears from within Kabuto. Along with Orochimaru, Sauske goes in search of the shinigami mask using which Orochimaru tears open the stomach of the Death Reaper, thereby releasing all those that were sealed inside the death reaper seal.
After this the 4 Hokages are resurrected and then the plot goes into the back drop, and finally Sasuke makes the decision that he will fight for Konoha and thus joins the battle.
This is the flow of the time line. So I see no part where Sasuke was lazing around or Tobi kept him under lock and key.