One thing works wonderfully, pure ALSA. To have multilple apps sharing ALSA, I just use dmix. As I use digital out, there is no mixer, but ALSA can provide one through softvol. It works really well. ALSA is already not that simple to configure/setup properly, but with pulseaudio on top, welcome to your worst configuration nightmares.
Here is the .asoundrc I use:
pcm "amix" #redirect the output to dmix (instead of "hw:0,0")
name "PCM" #override the PCM slider to set the softvol volume level globally
slave.pcm "softvol" #make use of softvol