Description
This is a bug that's been present since the original Witchery for 1.7.10: the sound files for the mod are usually in stereo and therefore don't have proper positional audio (e.g. if a mob sound plays, no matter what it'll play in both ears), which tends to be very annoying and makes it difficult to tell where a sound is coming from.

This is easy to fix, all that needs to be done is to convert the stereo files into mono files. In fact, I've already done this for you, here's a link to a 7z file with the fixed sounds included (I also trimmed and EQed particularly annoying sounds; I left anything that didn't need fixing). I would've done a PR, but honestly I can't be bothered to do that today and this is simpler:
https://mega.nz/file/daJ2mYyR#HCfjR_yeNL9S2U9oBCzj8rYTcG421nN7S2T4lSlUqOw

Environment
The issue is present in Single-Player and Multi-Player

Other mods
The issue is present with just Forge and Witchery: Resurrected

Steps to Reproduce

1. Listen to a mob's sound effect in-game.
2. Notice that no matter what it always plays in both ears, even if it's off to the side or behind you.
3. Be mildly irritated.

Hi! Sorry for the very late response.
This should be possible with a simple resource pack. I created a zip file with the proper structure and files. I'll upload it here, and maybe on Companion page under additional files section. You could also upload it yourself to Curseforge or Modrinth as a resource pack, so you can take credit from it.
Witchery Mono Soundpack.zip
Just drop it in the resourcepacks folder and enable it from the in-game menu

I did already make it as a resource pack, but I figured it'd be best to incorporate it into the mod directly since (from my own experience) people don't really download resource packs for things like sound fixes.