Oh well, I can see your point musically, but I was considering Astonishing the song in the context of the entire album, and how it serves as a big finale - I'm happy that it ends like that and not with Our New World or even the somehow triumphant, but less intense, Hymn of a 1000 Voices.
I know the song is made up of reprises from other temes of the album, but the ending is a cool and bombastic reprise. After all also Gran Finale from Six Degrees ends with the main theme (wanna know how a 42 minute songs end? you basically already know 6 minutes in, as the Overture ends), and Razor's Edge eargasmic solo follows Someone Like Him's melody, so I'm happy with the way Astonishing ends even if the song itself is nothing new and doesn't present, within the standalone song, much tension to serve a contrast to the eventual ending.