I do see what you mean, Ron. But I didn't take the Aragorn cliff scene as an indication that he's human and therefore mortal. Quite the opposite, I took it to show that he's superhuman and can even fall off a giant cliff, and less than 24 hours later stay up all night wearing heavy armor and killing orcs! It made him seem less human to me, in other words, just as Gandalf's surviving a giant fall indicated that he was not, in fact, human at all. As to making the movie less predictable, I did not for one second think Aragorn was going to die. Therefore, the only possible outcome was the one that we saw. Did anyone have a different reaction?

I love irony myself, and indeed laughed out loud when Scatman Crothers took the hit, but on later reflection wondered if all that screen time was necessary for the laugh.