Well, you've also got the problem of the fact that energy disperses, so by the time a laser blast hit ground it can be over 100m in diameter. The Deathstar was the "least" in the terror department. You have the world destroyers(or some such thing) which converted any element and spat out attack craft in a fully automated matter. Then there was the Suncrusher which had indestructible armor(Han Solo flew it THROUGH the bridge of an Imperial Star Destroyer and out the back of the command tower without a scratch on the craft. Not to mention that it was armed with a torpedo that when fired into a star caused the star to go nova(Kyp Durron Destroyed the Carrida system, the main stormtrooper training ground, in this fashion)