Multiple artillery would negate high angle of attack ? Plus after a steep dive, dragon would then then bleed speed pulling up which is the ideal time to shoot. I remember that German Stukas were most vulnerable after coming out of a dive bomb attack. Far better for NIGHT attack when Artillery is nearly blind, all Artillery positions were easily spotted in day time in fixed locations. Even better have siege army fire flaming boulders into the Artillery positions both to illuminate them and attract the enemies attention. But you know Americans they love giant explosions and have to make battle exciting.