Hello.
I would like to report a huge bug. I believe people might not notice it, if they arent playing for immersion whatsoever (own music, group comms, youtube or tv show on 2nd screen etc). But if you create a new character (if you are returning player like me), and want some multiplayer experience in WoW while leveling, and want to find some immersion with the game. To connect with it again, you cant. You will quickly notice there is something wrong. Especially if you would like to be a healer.
First i thought its just my problem. Then i reseted everything to default to no avail. Then i found several other threads about it. Now in a slow paced dungeon in timewalking random dungeon on low levels, i was able to stop the group and ask them if they hear other players sounds or only themselves and enemies cause i just could not believe people dont notice that and wanted to make sure its only small unlucky group of players.
They all confirmed after testing, and checking, that they indeed also hear only themselves and enemies. They also hear abilities i cast, only if im casting on them - like buffs. But other than that, its like an old mute black and white movies when you watch your allies and happen to be a healer.
Its so bizarre, so disenchanting and so sad to see it in live version of the game… Its even more sad, that other threads about it are like 2 years old.
That said, i know noone will care, but its also part of feedback that might interest someone: I wont be coming back to WoW anymore. Cant even feed nostalgia anymore, cause all what was good is like mutilated. All i can experience is agony of all that was nice. Where is the Blizzard quality and care for athmosphere of the game? Do you guys care only about systems now? Just numbers and hooks? How many returning players you are repulsing with this mutilated content? I mean, how can missing sound be not important during quality check? Are dev teams dying in Blizzard? So you can focus only on burning issues for the raiding and streaming people (who dont care about WoW sounds anymore anyway)?
Im utterly disapointed. One best thing WoW had in my memories was the quality and athmosphere. And you killed it with these 2 years old reports of this horrible bug that i see today.
P.S.
In one of the other thread about this problem i have seen mention of some official blizzard response, that it was intentional change to make other players sounds lower in volume than your own. But its either misunderstunding the real issue (no sounds of other players whatsoever, or perhaps 0.5% volume) or a bug, where someone overdid the “adjustment” of these volumes with a typo or other bug in code. I dont know, but its horrible and its been around for 2 years, and its not just small group of players. It affects everyone or majority of players (what are the odds whole random party of random dungeon when tested, confirmed it affects them aswell, for this problem to not be affecting everyone? My bet is that simply not everyone notice).
P.S.2
Other option is that people who are grouped (and not grouped via random dungeon system) dont experience that problem? Thats possible. Im returning player, and only dungeons i can do while leveling are with random people via random dungeon queue. That would explain why not many people notice the problem, if they can hear others properly during their raids. I dont know. Maybe noone listens to WoWs sounds anymore.
edit:
Just wanted to add, that in companion dungeons i can hear the NPC party sounds very well. So its not just the fact that i am in instanced content. Its the instanced multiplayer content that basically mutes the sounds of other players for some reason (unless they cast something on you specifically).
Do we really need to do single player content in WoW to get the nice feeling of the game? I doubt anyone pays for expansions nor subscriptions to play single player game. So why the multiplayer aspect is left bugged for so long? 
You actively pushing players away from the game.