I mean that I hope to stay at a distance and kill things with a bow. So monsters hopefully won't hit me, so the first two armours wouldn't do as much. But the third armour would be able to chill ranged attackers. As I will have neither cold offensive spells nor a holy freeze merc, this might be good. But I just don't know which cold armour is best, so the main reason I'm using this one is that I haven't used it before ;) .

Well, staves can be equipped by any character. And I think mace mastery does work on staves. And there are some staves that do have damage boni, and are obviously intended for hitting people. But they are still relatively weak.