There are six Guild Wars Necromancer specific insignias for armor. This profession uses most of these quite frequently. Depending on what they are doing in the game, they should be able to use an armor set specifically for that purpose. For instance, when going against foes that deal holy damage, finding the armor that uses the PC Tormentor’s insignia would be best used to block that type of attack.
Blighter’s: Armor +20 while affected by a hex spell.
Bloodstained: Reduces the casting time of the spells that will exploit corpses by 25%. It is non stacking.
Bonelace: Armor +15 against piercing attacks.
Minion Master’s: Armor +5 while you are in control of a minion.
Tormentor’s: Armor +10 and holy damage you receive increased by 6 on chest armor, by 4 on leg armor, and by 3 on any other armor.
Undertaker’s: Armor +5 while your health is below 80%.