I had sometimes bad openings but I have to say that the deck works pretty well as you described (Sense Demons and Witchwood Piper saved me more than one game when Plot Twist didn't pop out).
Not having Dr. Morrigan and Cairne Bloodhoof i tried using Arch-Villain Rafaam ( just for value in late game having used all the Plot Twist ) and Safeguard as replacements maintaining the deck consistency. I think that also two copies of Safeguard alone can be a good budget replacement for the two legendaries.
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