If the Dragon Mage has taken Armor Lore and/or Mentalism Lore then he will already have massive physical armor from this Combat Art even without needing to take either of the Protection mods. Therefore they can be skipped if the Dragon Mage is mostly staying out of melee range. If he does take the Protection mods, combining them with Armor Lore, Mentalism Lore, and Toughness, he can achieve the highest physical armor values of any character in the game.
If using double or triple buffs the Dragon Mage may wish to take the gold mod Flux to keep regen times down. A more focused or defensive mage may prefer the even further increased chance to block enemy spells with the Runes mod.
Pros and Cons
Highly valuable defensive buff
Potential for colossal physical armor values
Blocks enemy combat arts and boosts defense, and stuns those that get too close