At what point do ADC's stop being champions who deal "sustained damage", instead qualifying as burst-assassins now? Playing champions like Miss Fortune, Vayne, or Draven, It's not hard to blow up the enemy in a little over 1 second; fight's over before it even started.
Sustained damage and burst damage doesn't have much to do with how much damage you actually put out. Sustained damage is self explanatory, any champion who's able to maintain their standard of damage over a long period of time are sustained damage dealers. ADCs will usually never run out of damage when attacking. Burst damage is thus self explanatory, any champion who usually only has windows of damage dealing over a short period of time are burst damage dealers. Assassins will usually have a period of time where they won't have nearly as much damage as when they offload their damage.
Right now you're looking to address the fact that ADCs tend to deal the amount burst assassins do consistently, so there is no such thing as a 'threshold' for 'sustained damage'. Besides, ADCs and Assassins have different roles and playstyles. ADCs are the easiest to kill and Assassins tend to have mechanics who somehow allow them to 'bypass' the ADC's monstrous damage, whether that be a dash, hard CC or invisibility to name just a few. Thus, some Assassins who are lacking in either the burst damage category or 'bypassing oncoming damage' category are considered weaker and likewise, vice versa with ADCs who are able to 'avoid' the bypassing of their damage or able to 'avoid' portions of burst damage from Assassins are considered stronger. This is essentially what the meta is based on.
