Morollan was a bit of a special case; he was in the way of Mellar, not many people know who he is, let alone he has a GW, and he was set up. Nobles might know, but doubtfully a Jhereg assassin. If Vlad made a few examples out of assassins they probably won't risk their souls for Imperials. I think Vlad'll be mad because Cawti deliberately made Kiera promise not to tell Vlad he had a son. It's one thing to not tell him for his safety, but another to forbid one of his oldest friends to tell him what's going on. Another thing is, that whether she's still in with Kelly or not, she believes in his cause and what he's trying to do, and I doubt she'll raise VN without attempting to instill what she believes in. Vlad would not agree with that.