shaco is an assassin bud, dealing sustained damage after your burst doesn't make you a melee adc, anyone building ad can do sustained damage after burst because you will always have auto attacks as that scales with ad. Shaco is the literal definition of an assassin, Invisability, must be behind you for maximum damage, a point and click slow. If that isnt an assassin idk what is. melee adcs do a lot of sustained damage during a fight and usually cant one shot anyone unless extremely fed (trynd, yasuo, fiora, maybe riven) assassins do all of their damage extremely fast on a single target and attempt to obliterate them and that is where most of their damage comes from (shaco, zed, leblanc, akali, talon)