^Actually, WB Animation productions like this, and others with Andrea Romano as the voice director, often do get the performers to record together in a group whenever possible. Although I saw a preview feature for this and I think they showed the actors recording separately.
As for this week's episode, I didn't recognize the guy who turned out to be the killer, but somehow I was able to guess he'd be the killer, or at least might be, just from the way the camera focused on him when he first appeared, the way it went out of its way to give him a close-up and call him to our attention.
And I find it amusing that Ioan Gruffudd was basically playing Reed Richards, a genius inventor-billionaire. Well, if Reed were a celebrated womanizer instead of an uber-nerd. Maybe Tony Stark is a better analogy.