To address this for a moment, you cant prove a negative like "Nale hasn't been good for the story", so if you want complete proof one way or another, it pretty much has to come from you.
Besides that though, id like you to point out a few scenes before Blood Runs in the Family where you think Nale personally is integral to the way the scene played out, and where replacing him with some other, similar threat would result in the characters developing differently. The only one I can think of is the "Damsel in Distress" moment currently under the knife. That's... not a lot, considering how often he has appeared.