With the best will in the world, I can't identify anything in Janek or Vickers that made them any more rounded as characters than "I'm not here to make friends, pal" Fifield. Vickers, I suppose, is afforded some ambiguity by the evident intent to leave the question of her human/robotic nature in question, but she is still presented as an off-the-peg corporate *****.
I think Noomie has been slightly underrated as Shaw. The role and her performance is not destined to become as iconic as Sigourney's turn as Ripley, but what could? I think it would have been a mistake to try to recapture all of that magic. I find Shaw to be likeable and resourceful, and to be quite a good "barometer of atmosphere", which is important for actors in these sorts of movies.
I do hope, however, that Ridley and co feel they have given the Christian hypothesis enough of an airing in this film, and that they will set it aside for the next. It's not that I object to it being addressed, but it seems to drag what should be a conceptual sci-fi film into murky waters.