The question arises though, which effect of shrouding kicks in? Is the attack nullified or does it scatter double?Yes, and yes. His orbital bombardment is considered a shooting attack, and thus, our shrouding may protect us from it.
Depnding on his rolls he could hit himself xDMy my. If he rolls a miss,you roll another D6
Double that.
Thats a theoretical 36 inch scatter. Poor shot indeed.