Boromir

Why does Tolkien choose to dispense with Boromir so early in LOTR? He is clearly a character based on heroic traditions as are several of Tolkien's characters. Did we really need another traditional hero? Why did he bother to introduce him at all, if he was going to die so early in the narrative? Remember that Tolkien could have written this story without needing Boromir in any scene at all, so what purpose(s) does he have in including this character?