So what is the AC/CMD of an instantaneous fireball streaking towards its target?
Love the concept, just not sure how I'd implement it in game. As others have said, realistically (hate using that word in conjunction with an RPG, but I've already used it so there you go) you're better off shooting the caster while he's casting it.
Is the fireball of a high level caster harder to hit than a fireball from a 5th level caster? It would seem very difficult regardless of level, and I don't think I would want it to be commonplace for high level archers to shoot high level casters' fireballs out of the sky. Loses its cool factor. Thoughts?
I'd say 10 + caster's caster level + caster's key ability modifier + 8 (for size fine). At least.