Having a 3|0 card for 0 cost is not OP at all. Next you'll be saying that Cat is OP since it can die multiple times.
You forget S. Cat requires quanta to trigger death effects, whereas Spark and Ball Lightning do not, their death is automatic. Compared to S. Cat, its ability to die is so cheap, costing no quanta to trigger its death, while S. Cat requires multiple uses of it's ability to even make a dent in the Entropy-Death strategy.
Updated calculation
3|5 cost for attack, -2 for 0 health and -2 for the upgrade = 1 cost = 0quanta + 1 card
Sure, it makes sense stat-wise, and the cost-to-stat is fair, but the fact simply remains that it dies upon use, that should be considered as an indirect ability of its own, an ability that has no cost, is automatic, and cannot be stopped by the opponent player. Schrodinger's Cat can die multiple times, sure, but dying requires Entropy quanta for triggering death effects, which doesn't make S. Cat overpowered at all. Combine Spark with a well-placed Fractal, you get insane Bone Wall boosts, Vulture boosts, insane waves of death quanta coming your way with soul catchers. Adding the fact that it behaves like a temporary army of 3/0 creatures, that just adds insult to injury. Yet, the card fills a unique niche. The fact that its a temporary card with 0 life is what
makes the card so effing cool, which is why I don't ask for its life to go up, I just ask a simple decrease in attack to make up for the fact that it
dies in a more convenient way that Schrodinger's Cat. I mean, would you rather have those death effects be compounded with a whopping 3x # of sparks amount of damage, or something a little less potent?