Attachments that were not self-targetable (Healing Presence etc...) can be attached to self via interaction with enemies holding Mystical Wyrmhide. finding funny combos is fun...
Creative! I pulled a similar thing once when my priest had been hit with Taunt when I was in desperate need of health and wanted to play a Bungled Heal. Since I couldn't self-target due to taunt, I targeted the enemy character, and of course his nearest enemy (my priest) also healed .
Dissolve Armor discards before damage, but not before blocks. Melt Armor should discard before blocks. It's a good question as to whether Dissolve Armor's discard effect should come before or after damage. In general, I would think damage should be applied first, but that's only a convention. Probably the best thing to do is clarify the order on the card.