[burrahobbit]

Depends on what you mean by "hadn't captured Merry and Pippin." If the Orcs had attacked and then been fought off, mostly it would have been the same, but without Ents. If the Orcs hadn't attacked, Boromir still would have tried to steal the ring and Frodo still would have run away. In the first case Boromir may or may not have died, in the second he certainly wouldn't have. With Boromir alive the company would have been more inclined to head toward Gondor to offer and aid that they could. Would they have done anything in Rohan? Perhaps they wouldn't have been quite as hasty and thus wouldn't have been found by Eomer. They certainly wouldn't have gone into Fangorn, and so they wouldn't have found Gandalf or any Ents there. Maybe they would have been found in Rohan by Galdalf, and perhaps Gandalf could have spurred on the ents. I generally don't think it would have been much different if Merry and Pippin hadn't been captured.