Too nimble a flier? You think that the Horntail is more nimble than attack choppers? Because, Zilla destroyed all of the choppers that were attacking it by hitting them. That aside, I seriously doubt that the dragon could "dodge" the fire considering that it has a spread of about 60 feet and also launches an invisible gust of wind that can launch multi-ton cars into the air.
What is a spiked tail going to do? Zilla made a street full of cars fly up into the air by screaming at them, dodged hellfire missiles, was unharmed by a barrage of 50. caliber armor piercing rounds fired from attack choppers and rear mounted LRV's, took twelve anti-armor missiles from F-16's without dying, yet you think a spike on a tail attached to a creature that's a quarter of its size is going to anything but annoy it?