Raubahn losing his arm was not about his fighting prowess, which is why it hasn't really been affected.

For those who missed the connection, Raubahn lost the arm that he always carried Nanamo on. He lost his arm in the events surrounding Nanamo's "death".

He lost nanamo and the arm he used to lift her up and support her. It was the start of Nanamo realising she relied on him too much and the start of her development into a leader into her own right.