There are games that can pull off a silent protagonist quite well, aka HL.
But Dishonored has a basic failing of putting the silent protagonist forward as an actual character who is emotionally involved in events, has a backstory etc. They make him very much an involved character instead of the usual player vessel that a silent protagonist serves as. Because of this Corvo who is kind of a central part of the story and should be emotionally tied to it, actually falls apart because of the constant 100% silence. The fact that you are presumed speaking in certain events when choosing one or two lines of dialogue doesn't help either, as it implies that Corvo is quite capable of speaking to people yet at important moments of the game is a dumb mute, instead of actually being a human with thoughts and emotions of his own.
Ultimately I agree with the OP, yes in Dishonored the silent protagonist hurts the overall narrative and hence the game.