I think even the dumbest creatures are a little more productive than shooting at a tank with a rifle, if there was even a dozen riflemen I'm pretty sure they'd find a way to enter the tank and shoot the driver with a rifle, just like a thousand peasants would find a way to disable a dragon and slay it with nothing but pitchforks and common sense. I think the original mechanism works just fine where dragons easily slay tens of peasants at a time, even the toughest and strongest of dragons couldn't handle more than that except if they threw themselves at the peasants and rolled on the ground, forfeiting any chance of defense against retaliation. Your analogy lacks depth.
