I agree that the vocal melodies of The Knife isn't the main feature. It is the prog elements/instrumental parts and a sense of dramatic arc that make it a great song
Dusk is more reliant on the atmosphere than vocal melodies which I agree
White Mountain melodies is fine although perhaps it's not exceptional. What really appreciate about the song is the arrangement the "Thin hung the web like a trap in a cage," with the guitar appeggio, which builds up the "Outcast he trespassed where no wolf may tread" build up of instruments with the keyboard appegios which leads to the rising melody of "Plunging through forests and snow-storm." and the sudden drop in the instrumentation leaving behind just the acoustic guitar which I find beautiful. What I like about that song is the fluctuation in intensity in the arrangement more than the vocal melodies per se.
I still love the vocal melodies of Visions of Angels though