The issue can be put on resolved. The missing gunsounds and animations were due to a installed - but not enabled flashbang/stungrenade mod, strangely enough.

Interesting to note was, that people with the mod installed could hear each other, whilst being "mute" to everyone else, and vice versa.

Removing the mod, and verifying the gamecache after that solved the problem

if you shoot the lightbulb in the casing directly you only need one shot if you hit

have you tried to disable the "steamfriendly UI" option in the configuration?
i accidently enabled it for a while, and i had my chatbox etc not displayed either in Multiplayer or Campaign/Scenarioes

In this state, Multiplayer is basicly unplayable as long as you dont have the most, and I reapeat THE MOST expensive latest i7 cpu. Dont even try it with hexacores or such from AMD like I do. You get screwed over from Bohemia BIG time.
12 Fps in MP even far away from the Actual warzone? Check. 60 Frames in singleplayer with Max Graphics? Check. This is just WOW, and it takes my main aspect of fun out of the game, namely MULTIPLAYER.

They could at least acknowledge the Issue itself to give the signal that the performance is indeed an issue for them. As it stands now Im kind of getting the eerie feeling that they cant do much about the performance whatsoever,not even in the future. Im afraid that they ignore this because they wont do anyhing about it anymore. period.Since I cant code and just have a mediocre understanding of the engine I can only guess, so what do you guys think?