It is when its John Hurt, and promotes the programme through him. Or wasn't there a whole lot of (retroactively pointless) debate about what John Hurt's Doctor was gonna be over the summer?
But they did not
promote the programme through John Hurt.
He was not mentioned and his face was not visible in the teaser trailer. His name was listed in fifth position on the official poster, which featured a tiny John Hurt figure in the middle of two towering Matt Smith and David Tennant pictures. He didn't get more interviews or have more media presence than Jenna Coleman.
What you're talking about here, it seems to me, is the amount of speculation among fans, but I can assure you that it's not on the forefront of Stephen Moffat's preoccupations and has very little to do with his casting decisions.
Hardly a small role though was it?
It was a pivotal, meaty role, which is why they picked a talented and charismatic actor to play it. Thinking that they were counting on the legions of John Hurt fans to boost up Doctor Who's
viewing figures, though, which is what stunt casting is, is obviously delusional.