My two cents: I have been having issues hearing or talking to one specific friend but could talk to just about everyone else. Last night I was talking to a mew person. Everything was fine, then I got booted with an error code I simply cannot remember. I restated Destiny and teamed back up, but voice chat didn't work. I rebooted the PS4 and tried again, no luck. Today, I got an invite from another person so I joined. Again no audio from any of the five people, and I don't think they were hearing me. I went to settings checked my microphone level. It works, I routed speakers to the headset. That works. Without any changes to my local network from flawless operation, to the error code last night, and now, no chat...
I believe it has to do with NAT settings.