Fucking finally... I found the problem:
Stewie Tweaks:
; add a minimum interval between player pain sounds
bLessFrequentPlayerPainSounds = 0
I had that on 1 and the iMinPlayerPainSoundIntervalMS value was like 100000.
I still don't understand why I haven't heard a voice line at least once though. What a cluster fuck...
Still got a question though regarding Dialogues
Is it normal that I only hear one specific Power attack sound every time I load a game? Is that normal behaviour? Does the game choose one from the response tree and stick with it until a new game is loaded?