Do any MMOs actually host some type of voice chat system these days?
WoW did or does. I want to say that either EQ or EQ2 did or does at some point, but not sure. But, these options are generally really crappy compared to actual voice programs like Teamspeak or Ventrilo. Bare minimum, any voice chat system
needs the ability not merely to adjust your output, global input, and mute specific individuals, but also adjust the incoming volume of specific individuals as well. Sometimes people sound mostly fine but they come in at 175% and someone else is at 40% and they both talk lots (and sometimes important things) so you can't just mute them but it's really annoying to get a volume that can hear one without blowing out your ears when the other talks.
When third party systems also offer things like mixers and adjust specific frequencies, game-integrated voice chat just becomes a pitiful shadow whose only benefit is convenience when you're doing something without your friends, which means it's likely not so hard that you need the celerity of voice chat to coordinate in real time.
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And wow, I do not want to hear 40+ people bullshitting in voice in GW2 zerg, nor to do I want to spend the time muting them all. If ArenaNET does ever bother with it, they could take a page from PS2 and have separate raid leader, raid, group leader, group channels so you can mute some in one click without muting the important stuff. (Though it's not a big deal anyway since I haven't played GW2 much these days.)