Sorry, but this will be very sound specific:
It is the sound supervisors' job to tell the director that the guy in the mask is inaudible, and it's the director's job to listen and either say "Don't worry, we'll get it clean in ADR" OR he gets it clean on set ... this mumble-fest happens too early on in the show to risk peeing off your audience ... luckily, I'm a sucker for all this alternative reality malarky so I stuck with it, but many won't.
... and yep ... the bar is set mighty high with "Dark"