I have had that problem on xb1 for quite a while as well... Maybe a console issue in general. About the only thing I haven't tried is a full re-install of the game... Don't want to even think about how long that would take.
"It is a lovely language, but it takes a very long time saying anything in it, because we do not say anything in it, unless it is worth taking a long time to say, and to listen to." - Treebeard
The DNS fix listed above seems to have fixed the issue for me. I applied it maybe two months ago and since I have only had two issues with voice chat. One being an "unable to determine zone" message as I joined a battleground and it would not let me rejoin the group channel. Another where I got kicked from group chat during a port but was able to rejoin immediately without issue.