When I cast Healing Burst, it healed my team but also triggered an enemy's Armor card. The enemy rolled a six and used up his Armor and was not healed. I'm not sure if Healing Burst is supposed to heal enemies in my range, but even if it does, it should probably not trigger Armor.
Wait. Are you quite sure it was Armor? Because it's known that "hostile" spells will trigger Blocks, and of course Blocks completely negate whatever was coming. Your own healing counts as "hostile" to the enemy because it can't possibly know that your card will help it (as opposed to, say, Misguided Heal which could kill it). So, was it Armor or a Block? Edit: Yes, Healing Burst is programmed to heal enemies in range, as indicated by the phrasing on the card (it doesn't say "ally"). Some cards have downsides like that.