Guitar and bass actually have Expert charts for the animations, and I think Blitz uses the animations for drums and keys. Vocals get nothing, but there's usually nothing to chart at those parts anyway.
That would explain why the drums are charted in the intro of We Are the Nightmare.
 Dizzy Mizz Lizzy  Dover  Guano Apes  More Miley Cyrus
 The Rasmus  The Veronicas  More Volbeat