This spell does 2 damage without spending a charge; you're only forced to lose a charge on revealing a skull, or if you want to do the 3rd, targeted damage. If I'm not mistaken, that is a first for mystic spell assets. Its existence therefore reinforces the potential for a dedicated willpower fighter.
On the other hand, 5 xp is a lot, especially when they decided to reprint 0xp Machete in the same set, which similarly has access to infinite conditional 2 damage actions.
They did not reprint Machete, and the new Machete must exhaust for +1 damage. Therefore, I believe a more appropriate comparison for this card is the new Sledgehammer (3). From that perspective, Cosmic Flame (5) seems easily worth its xp cost. It grants +2 willpower, unlike its guardian counterpart, which offers no bonus on the 2 damage/action mode. It offers higher damage per action. It also offers the utility of splitting the 1 damage across a second target, and even damaging an aloof enemy without engaging. All that, and it occupies only one arcane slot, compared to sledgehammer's two!
For those with dreams of using willpower tests to shoot enemies forever and ever, look to this card.