I know that several members of the cast can speak English fluently, Sidse and Birgitte in particular, but the have dubbed sterile precise voices over their characters.
Sidse was perfect in Westworld and Birgitte in Game of Thones and Midsomer Murders.
I mentioned this about a week ago, C@C. I said that i lasted about 15 mins into the first episode before i switched to sub-titles, which i stayed with through the entire series - which i really enjoyed. I know it's been a good number of years since we heard their actual voices, but it all sounded rather strange when dubbed.