Sure, the right to confront one's accuser is important, but historically, dying declarations have been deemed important and been given much respect. Yes, someone could lie at that time; likewise, one could be in error as one accuses someone with one's dying breath. But last words are facts, like any other facts, and should be weighed by a jury.
In Indiana, a dying declaration ended the political ascendancy of the Ku Klux Klan in the 1920s. Grand Dragon D.C. Stephenson, who bragged that he ran Indiana from the shadows, took a fancy to a young woman named Madge Oberholtzer. When she rejected his overtures, he lured her to his home, kidnaped her, raped her, and finally poisoned her. It took her two weeks to die (of mercury poisoning and kidney failure). During that time, she gave a detailed statement before witnesses of what had happened to her. Stephenson was sent to prison and the Indiana KKK went from political powerhouse to virtually nonexistent overnight.
Would Justice Scalia say that Oberholtzer's sworn testimony from beyond the grave should have been excluded at trial? Much as I admire his legal acumen in most things, I think he's way off base in this case. I'm with the majority on this one.