I don't like N'Diaye in a midfield two - as others have said, he likes to break forward a lot, leaving us with essentially only Neves or Saiss in the center. I can see the logic in games where we're expecting to be breaking down opposition teams set up primarily to defend (and the Hull game was one of those, really), but in games where the two teams are more evenly matched, it's counterproductive, IMO.
He'd have been a perfect number 10 for Jackett's 4-2-3-1, mind.