It would appear their resists are that of the suit they wear, at least.
A full set of normal armor (or almost for leather, as it's missing the cap)
studded: 10/20/15/15/20
Leather suit, minus the cap: 10/20/15/15/15
Ringmail: 12/12/4/20/12
Chainmail: 12/12/12/3/6
Platemail: 30/15/10/15/10
As a result, Consecrate weapon has only a little affect, and Armor ignore practically none (especially if you can use CW). On the other hand, Corpse Skin should do interesting things to the resists if your damage is the right type (CW, or an elemental weapon). A 100% poison (or consecrated) weapon, combined with corpse skin, against a chain suit wearing NPC should be downright nasty.
Has anyone tried to disarm the Invasion NPCs? I've not gone into battle against them with a weapon that has the property.