Further, if arc is always a 2d plane at the angle of the gun, then can a vindicator with demolisher not target models if the plane from its gun does not intersect the target model? I'm not sure what angle they're at, but even if it was a 10 degree angle, that means at max range (24"), a target would have to be over 4" tall to be a valid target (not counting the initial height of the vindicator's gun, so it would actually be greater than 4"). I had always assumed that vehicle arcs were 3d spaces bounded by the angles, not 2d planes from the gun's point. Is that wrong?
And, I would definitely let an opponent World Eater player do that, but I would never do that if I was playing as World Eaters.
Edited to add: Ordinance allows you to roll an extra die when rolling for armour penetration. Haywire replaces the armour penetration roll. So one rolls a single die on the haywire table because it replaces the armour penetration roll, so there is no roll to have a die added to it. Is that not clear?
Edited by Ficinus, 17 September 2020 - 02:48 PM.