I agree with neferhet remarks, and would add that, fluffy speaking, Iron Warriors are closer to Khorne than to other Chaos Gods.
I would then make a first CSM unit with Icon of Vengeance, and the other (close combat oriented) with Mark of Khorne (or even swap them for Berserkers).
Why the Spawns instead of an additional Daemon Engine (Maulerfiend or Helldrake, for instance) ?
I would then make a first CSM unit with Icon of Vengeance, and the other (close combat oriented) with Mark of Khorne (or even swap them for Berserkers).
Why the Spawns instead of an additional Daemon Engine (Maulerfiend or Helldrake, for instance) ?