Wild Harmony is an instant ability that gives you the versatility of dealing arcane damage (which can be combo'd with a card or two) or healing damage. Instantly. Even during combat. So if I am in a situation where I have 4 ready resources, which isn't too likely, and an ally or hero of mine is a proposed defender, I can play this card and destroy the attacker before he deals his damage packet. I would probably straight up play this card if I needed the heals or the damage- for each resource I pay to play this card I am getting 1 damage or 1 heal. Would have been nice if this was a portal card, but then again it is a common. I'd consider it if I needed to fill a gap for a cost 4 card.