What if Isengard joined forces with Gondor?

[Raynor]

There would be no Uruk-Hai because Saruman created them because he was to "build an army worthy of Mordor".

Debatable. That command from Sauron appears only in the movie. Ever since he became corrupt, Saruman wanted to take Sauron's place. Even after he is "ensnared" by Sauron, he still keeps his plans, as he confesses to Gandalf. It doesn't look like he made the uruk hai to help Sauron, quite the contrary case could be made.

If Saruman didn't became corrupt, he would agree to attack Dol Guldur in 2851, and not 90 years later, when it made little difference. It may be argued that the attack could have come sooner (perhaps 1100 when they first found out there was something fishy) if he and Gandalf joined forces and even the ring might have been found sooner, who knows. If there was proper communication between Gandalf and Saruman, Saruman might have inferred quicker about Bilbo's ring being the one. Or maybe they would have tracked it together sooner than Bilbo (Radagast would be more helpful, if Saruman would stick to his good side and offer him a chance to get involved in this.)

The best that they could have achieved would have been to kill Sauron, again and bring the ring to Mount Doom, anytime sooner than 1300, when the nazgul reappear, or the latest in 1980, when the witch-king returns to Mordor.