Sean Bean's mispronunciations could be chalked up to lack of proper directing, it's not intrinsically his fault unless he refuses to do any retakes. Everybody has an accent so that's an odd request. The woman from the First Look videos doesn't really have a great voice due to the notable 'vocal fry' (I think that's what it's called). She serves the purpose of First Looks but I wouldn't have her do the in-game narration....and Sean Bean, mangling them all nicely.
Dear Firaxis, next time just hire the generic voiced woman, not a star, to do the voicework.
And for the love of god nobody with any kind of accent. I'm a native english speaker and his mangling makes my ears bleed. I can't imagine what the folks that aren't native english speakers go through.
Speaking of voice acting, Seondeok has a voiced dialogue at the trading screen in the Cree video. I haven't watched the streams but is this new? I doubt they went and got all the actors back to record new trading dialogue so I'm not sure what to make of that.