Everything in the looting system is TOTAL lottery. Think of the system as a 100,000 sided die. Let's say that one-fourth of those sides are rusty cutlasses, and there is only one side for the World-Eater Blade. This is exactly how the games chooses what weapons you will get. When the creators created this system, they gave each weapon a certain probability to show. If you want to go along with my "die explanation," the chance of looting a World-Eater Blade is 1/100,000. The way that this is said is that you will get a World-Eater Blade will show up every one in 100,000 times.
Hope this helps!
