I have been thinking for some chapters why none of those two servants have done nothing till now and no one on the palace finds it strange, this happens. Assasin of black is obviously busy for now corpse searching and does not care.
Now let's see which important role Assasin of black plays. Stab someone at an important part, maybe.
About Astolfo it makes me wonder if it means that he is a fake hero like Sasaki Kojiro in Fate Stay/Night or just the typical master looking down on servants in general.