Mirror image (and glamour) does not protect units

[PvK]

I think overlapping scale mail is not necessarily what is meant by Dominions' Scale Mail (or - ick! - D&D). Maybe they just mean cloth or leather with some scales on it, not overlapping, which would (depending on how much space was between the scales, and how thick they were) likely be less protective than good chain mail against some kinds of attacks. Note that Dominions (like - yetch! - D&D) also has an armor type unhistorically called "Plate Mail" which is not the same as Plate, and maybe that is more like overlapping scale mail?

However, if Scale Mail does mean overlapping metal scales, in general I'd agree that it would tend to offer more protection than typical chainmail.

And, back on topic, I think the Light Weight Scale Mail referred to here is actually the same type you can forge as a magic item using Air gems... not mundane metal armor. And (as a semi-relevant aside) for cavalry like Vans, encumbrance isn't even counted...