Voice communication can be one of the biggest selling points for any game.

Meh. Out of all the complaints that I've read, lack of a Voice Chat hasn't been one of them. You can get along quite well without using it.

But it's nice that you're getting involved! Welcome to VO.

But we can probably add it to some sort of interstitial popup, the 3rd or 4th time someone connects to the game, or something like that.

Why not do that the first time someone joins a Group or Guild. You know, when it's actually relevant?