I have a number of questions. First, why did Keene Curtis do the voice of Judah rather than the actor who is playing him (Michael McGuire)? That seems an unusual situation, to say the least. Granted, Curtis' voice was fantastic, and maybe McGuire has a high-pitched whine or something ... but if that's the case, why would he have been cast in the part to begin with?
I don't know the answer to those questions, but I've heard Michael McGuire's voice and my guess is that someone decided his voice wasn't satisfactory for portraying a powerful warlock, but then again what DOES a powerful warlock sound like?
Second, was Keene's voice dubbed? Was the hooded Judah Zachary Michael McGuire in that scene, or was it actually Keene Curtis.
No, it wasn't dubbed...
Could the hooded actor have been Keene Curtis, and then when there was a cutaway, was he then substituted with McGuire in the cut where Judah Zachary removes the hood?
Yes, that's how it played out.
Rewatching that scene refreshed my memory; very recently, in another topic, I had said that Keene Curtis was Judah's voice, but that wasn't completely correct because he also appeared as him, albeit with most of his face obscured by the hood.
What about the other voiceovers, such as when Gerard is hearing Judah Zachary's voice?
I haven't watched those scenes in a long time, so perhaps someone else could answer this question.