As of Beta 53.0, monsters with Armor have any DMG they would receive be reduced by 1, greatly increasing their survivability as they entirely block DMG from KR and effects like that of Undyne, making Armor monsters quite useful against Perseverance and Justice Decks. Cactus is also unable to trigger its effect without an ATK buff.
With Armor and 2 HP, Charles needs to take 2 x 2 or 1 x 3 DMG to die. For 3G, this somewhat makes it function like a tiny Mad Dummy. Using it in a Kindness Deck allows you to increase its HP, and thus its survivability, very easily. Be aware that it loses its Armor (and buffs) from Silence, though.