If you want to leave Ijat a tip for writing this DotA 2: Farming and Warding guide you can do so here.
DotA 2: Farming and Warding Walkthrough Attack Animation (Delay)
DotA 2: Farming and Warding Attack Animation (Delay)
As you all know, every hero in Dota 2 have different attack style thus different attack animation. This animation delay the attack. For example, ranged hero has longer attack animation due to ranged attack.
You have to consider the time to attack in order to get last hit. Especially ranged hero because their longer attack animation (this includes the time your attack travel to the unit).
Usually ranged hero is support, but maybe carry. But if you really wants to farm and get last hits. Try to be near the creep so that you attack quicker.