Something is amiss with how armor covers body parts in the game, in that some pieces of clothing/armor will protect body parts they do not cover, whereas some other pieces will
not protect body parts they are intended to cover, which is illogical and unbalanced. Here is the demonstration :
http://dwarffortresswiki.org/images/d/d8/Armor_Coverage_Chart.png-
Shirts, Cloaks, Coats, Dresses and Robes protects fingers and toes.-
Greaves, Leggings, Trousers, Long Skirts protects the toes.-
Masks, Face Veils does not cover the face.People have confirmed this by Arena testing.
Whereas Mail Shirts and Cloaks protecting the toes may cause only a minor balance issue (except if they are made of candy), Masks not protecting the face is kind of a problem : granted that Helms do not necessarily cover all facial features, it should be pretty natural that Masks did. Currently, wearing a Helmet + Mask + Face Veil will only add that many layers the skull, leaving the mouth, eyes, cheeks, nose and ears naked.
My suggestion is to be able to protect the face as intended, because this is only logical and balanced. This would resolve to an extent the issue that many people have of losing their Legendary adventurer to a hit in the face despite him wearing complete masterwork steel headgear.