KalKal
Superstar
Dragons are NOT comparable to nukes.
What makes nukes so devastating is the radiation. The radioactive fallout can stretch for thousands of square miles. They're more than just big bombs. Presumably, once Drogon left, that area he attacked was safe for any commoners or nurses to traverse. A farmer 100 miles away from that field wasn't feeling any effects from Drogon.
They have the offence of a Vietnam-era helicopter, but there's no way you could shoot down a helicopter with a crossbow/ballista.
You wouldn't even be able to shoot down a WWI biplane.
They're only "nukes" relative to the fact that they're in a world without gunpowder (and that they have apparently unlimited ammo until they need to eat).