To be fair, the voice options are pretty limited even without this taken into account. Make a half-orc barbarian and try to pick any of the existing voice options...yeah, none of them work. Not even close. Where's the deep, gruff voice? Where's the more mature scholarly voice? Where's the cocky young hothead? Of any gender? Seems to me Larian cheaped out a bit on the Tav voices, which is odd considering the custom character doesn't have many voice lines at all. Wouldn't have been (be...?) a monumental undertaking to make a few more voice sets, and then a more neutral voice set would certainly be a nice option too.
