Yeah, this is still bad. Doom would never let himself be talked to like how those demons are. And what about all of the technological superiority built into his metal armor? Abandoned for leatherfetish sorcery? Doom already HAS sorcerous implements built into his metal armor. This is just EEEEEEEEEEEEVIL wearing the SKIN OF THE DAMNED, OOH SCARY, ARE YOU SCARED, BECAUSE THIS IS TOTALLY SCARY AND EEEEEEVIL AMIRITE?. Bleh.
And Doom wouldn't torture the other FF members to get at Reed, not after all of the character development of the past 40 years. Original flavor Doom, yeah okay. Modern Doom has moved past that. He probably would keep them imprisoned, but in all other respects he'd treat them as honored guests . . . who just can't leave. That would mess with Reed without the added TOTALLY EEEVIL ridiculousness.
The ONLY thing about this that is in character is Doom gloating . . . but again, it rings false. This is Victor kicking a sick, three-legged puppy when it's been hit by a car. Doom doesn't want a victory like this. Doom wants a SCIENCE!! victory that he can show the world, because anything else is playing with a stacked deck, written in invisible ink, soaked in skunk spray, ON THE WORLD'S UGLIEST GUITAR.