While expanding a bit on the subject, to my own understanding language neutrality advises not to put language specific lines in a sound effect or music. Ever. Though greenskins’ (and monsters’ alike) words are gorgeous, such as in the goblin combat tune
Having them as separate effects is fine, though. When I master for my kids and friends I might use those to teach a bit of english, when I narrate for my friends I’ll skip them as english is not so broadly understood in my country. But I like to have a choice.
To OP, it seems to me that voice acting has been done mainly for the late involvement with Wizards of the Coast, just to add some shine to the gold. Though I’m a relatively new subscriber, it does seem that acting is such a minority in the syrinscape database that to a fast glance it could well be defined as a bonus track, not a featured album.
Personally, I prefer to act myself: I want to be the one giving voice to Xanathar, not some very talented professional my-fun-spoiling voice actor that would do a much better job than myself