[Autumn]

I think this is a bug due to the amount of arrows consumed but I would share my opinion here too while I'm at it:

When using an ability in Archer that consumes an arrow stack, it will consume 1 (for the skill) + the amount of targets hit, this means that if you hit a starbow on 1 target, it will consume 2 gust/fire/ice/stone arrows instead of just 1, likewise if you hit 2 enemies it will consume 3 stacks and so forth.

This currently applies to:

-Starbow
-Aerial Razor

I do think that the extra arrow consumed is a bug, but consuming 1 arrow per target hit is a little much for a skill with only 7 charges by default as well. My personal opinion is that I think it should only consume 1 arrow when using either skill, though I Think what is 'correct' is that it only consumes 1 arrow per target hit.

[Neus]

This isn't actually a bug, as far as I can tell, because the special arrows use 1 stack to hit the tiles that are in the target (IE, ice arrows create ice sheets); 1 stack is also used per enemy, as you point out, to apply the damage effects.