Another option to look at is the listening position. There's a slider in

/systemconfig > Sound Settings

that lets you set the listening position closer to the camera or closer to the character. The farther to the Camera side, the louder sounds are as you zoom in or swing your camera near a source. The farther to the Character side, the louder sounds are as your character moves closer to the source. If you're hearing bosses obnoxiously loud you might benefit from adjusting this slider. I personally have it set all the way to the Camera side, but this can still cause loud spikes when I turn my camera to run away, but on the whole this setting works best for me.