I just played a game where I was Doctor and there was a confirmed Witch Doctor, and a confirmed Witch (occupying the Neutral Evil slot). Because of the Witch, I can conclude there was no Cultist to start with.
On Night 2, I heal a target, and I see the message, "You prevented the Cult from trying to convert your target tonight!"
What does this message look like? It looks like a Cultist attempted to convert my target, which would be an indicator that on Night 1, the Witch Doctor successfully recruited a new Cultist.
As it turns out, no such thing. The Witch Doctor didn't recruit anybody all game long. The only cult aligned role in the game at the end was him.
Oh, so that means my target was attacked, and my heal prevented the Witch Doctor from converting and healing him, right? Nope. He was never attacked (or if he was, he received no notification).
The two most obvious interpretations of the Doctor's heal message are incorrect. I would propose the Doctor's message should read as follows:
"You prevented the Cult from trying to convert your target tonight!" for preventing a normal cult conversion.
"Your target was attacked tonight!" "You prevented the Cult from trying to convert your target tonight!" for situations where the target was attacked AND a Cultist recruited him, and for situations where the target was attacked and healed by a Witch Doctor (the player will not know which of these was the case).
[No message] for situations where the target was healed by a Witch Doctor, but the target was not attacked.