After working through the Blizzard forums, I found a workaround that will allow AEmotes to play the sound clips again.
I'm waiting on the ACE folks to reset my SVN password so that I can upload the patched version.
The workaround requires playing a "system sound" to initialize the sound layer before you can play a custom sound file; so you might hear the lil "minimap zoom" click in the background while the AEmote sound clip is playing. You really have to be listening for it, to hear it in the background. Not my favorite solution, but it works until they patch the core sound engine.
Seems that VoiceChat was pretty much thrust upon 2.2, as a complete sound engine rewrite was being planned for 3.0 (which would have included Voice Chat). As a result, VoiceChat is really more of a 2.2 "hack" that causes sound priority issues.
I'll edit this post when I've uploaded the patch.