I tend to think of how well various fantasy monsters *wouldn't* stand up to a mecha with a shoulder mounted 30mm GAU-8 Avenger cannon with the magazine backpack mounted.
Or how about a dragon legend inspired by a time rift that has an A-10 Warthog blip back in time just as its pilot fires the gun? Big, noisy, flying thin with what looks like clawed wings, it has a toothy mouth and it make an ungodly roar as it spits out its firey breath of destruction!
14 ounce projectiles with depleted uranium cores, fired at a velocity of 3,250 feet per second at a rate of 3,900 per minute. Burst rates are limited to 1 or 2 seconds. It takes a second to spin up to full speed so the first second's firing rate is on an increasing curve.
The magazine can hold only 1,174 rounds so the total firing time available (if it could instantly spin up to full rate) is just over 18 seconds at 65 rounds per second. So the typical total firing time available to an A-10 Warthog is somewhere around 30 seconds.
Sooo, how well would the Dresdenverse's nastiest physically tangible monster hold up to 120 rounds in two seconds from an Avenger cannon?
See also almost every movie ever made that has machine guns. Except for ones like the old Thompson with optional 100 round drum, you get about three or four seconds out of one magazine. If you want to see what a real firefight with full auto weaponry is like,
http://www.youtube.com/watch?v=ejD1Gml-ZGc