I would have gladly included Holy Terror if it was a Batman story as originally intended. I think it's great stuff, some of Miller's best work (I understand some of the dialogue and subject matter is offensive to some but that's not what I'm referencing here).
As for Batman/Spawn, I've never been clear if that's a Millerverse story or not. Wikipedia claims it's a "companion piece to DKR". Has Miller ever confirmed it's in his Bat-continuity?