A useless argument. Can be applied to just about every piece of gear, and every build option in the game.
+20 HP is a great benefit to everyone. HP are very important, and getting extra from items is especially so on lower-HP melee classes like Monks. Every character should try to get a Toughness item somewhere, in their ideal gear setup. Minos is simply the easiest to get source of that.
20 HP doesn't just matter if you get reduced to 20 or less. It provides a buffer for healers so that they can safely throw heals less frequently.