Armor hit probabilities

Originally Posted by http://gw.gamewikis.org/wiki/Armor

Each body location has a certain probability to be struck by damage. As crafting material requirements (from the same crafter) for armors of different body locations always have a fixed ratio, folklore has it that this ratio also correspond to the relative probabilities of each body location being struck by damage.

The five body locations and their "crafting material percentages" are:

Head - 12.5% (1/8)
Chest - 37.5% (3/8)
Hands - 12.5% (1/8)
Legs - 25% (2/8)
Feet - 12.5% (1/8)

Originally Posted by Vermilion Okeanos

Considering that, most people would add armor to chest and torso, and add radiant/survivor/etc to arm, feet and head.