This will prevent all of Doom Lord Kazzak's yells from appearing in chat window. Mod by Cidrei.
This addon blocks *all* of Doom Lord Kazzak's yells from appearing in your chat window, and replaces his audible aggro and kill yells with the sweet sweet sounds of silence. You'll never even know he's there until the shadowbolt melts your face.
!!!! PLEASE NOTE !!!!
Due to how this particular addon works, the zip file contains complete folder structure. To install, you just need to extract the zip to the top level of your WoW install directory. Feel free to poke around the zip to see that nothing malicious is going on. It's just important that the sound files end up in the proper place.
I'm guessing the audio portion will work with any client, and the text blocking portion only with English clients. If you want to localize this into your own language, the code isn't exactly complicated.