Yeah, most of the "huge damage" combos with this call for a 6+ card combo, often costing 50+ quanta in 3 or 4 different types. With resources like that I can think of a lot of different ways to deal ridiculous amounts of damage.
I'm actually leaning towards calling this underpowered. It's a mid-cost spell that does a max of 15 damage to the opponent (unless you combo it with something), can't be targeted anywhere but your opponent, and kills one of your strong attacking creatures.
One question though- in it's current form will this stack with dive? Could I take, say a 10 attack creature with dive, use fling on it, and then use dive to deal 40 damage?
Sorry if my question has already been addressed.
*edit: note that no creature with 10 attack and dive exists, I picked the number for simplicity, not game aplicability