Thats not to say, of course, that I don't like Hurt or his performance as the War Doctor. I do, and he did extremely well - it was the rare stunt casting that worked, and thankfully for that. Can't complain on him, he did more than solid.
That's because it was not stunt casting, it was simply casting. As someone famously said, stunt casting implies that you cast someone solely because they are popular with your target audience. Now, I'm not really "down" with the kids anymore, I don't know a lot about hippity hop and Snoopy Snoopy Dog Dog, but I am fairly certain that most kids don't hang around the playgrounds discussing how cool John Hurt is.