Idea Archer nerf

I think archer just needs a full rework more than anything. As it stands, archer is very overpowered with instakills and underpowered without them. Its place in deterring stalemates doesn't really help, because it means that archer can't easily be changed without reworking stalemates themselves.

Moving on, though.

This is an interesting idea, but it would have to be implemented while keeping in mind a few things:

Assassin is the landmark for this idea. Assassin is arguably one of the most balanced classes in the game (beyond ping), and the ability for players to block at a cost of the ability to attack, heal, or move very quickly is what balances it. Archer doesn't need to worry about being attacked, nor does it typically need to worry about its damage being healed off. Furthermore, while an assassin can potentially read these actions and attack through them, archer has no such option, seeing as it plays at such a distance that moment to moment actions will be nearly impossible to read.
Also, this is an extremely potent nerf to archer, and even combined with the second idea, archer will be less powerful overall. Maybe archer does deserve a nerf, but some maps' defenses are very dependent on archer, and like you said, archer holds a valuable niche with regards to stalemates. This kind of blanket change probably won't work, just because of the sensitivity of archer's niche.

Am I ever glad you put that "maybe" in the front

Archer doesn't need 128 arrows to be as powerful as it is. Archer currently has too many, I'll give you that, but a single arrow can instakill, so cutting that number in half doesn't exactly change much. All it means is archer would need to more frequently get its items restored by a medic.
The real kicker here is the sharpness. Sharpness I on a stone sword is more powerful than iron, and I'm sure you can guess how good sharpness II would be.

To be fair, there currently is a sound that plays for this. It's the sound of an arrow landing. I'm sure if you really wanted, you could increase the volume by going into audio settings. If you have it on max and it's still too quiet, you could increase your system volume and decrease everything except for the arrows.

Fun ideas. I still think archer rework > archer nerfs, just because nerfing archer almost always seems to either be insignificant or just decimates playability.