Would be basically scaling, each champion are elite, each elite veteran, and so veteran regular enemies.
Example: For defense phase like reprogramming during CoE story, the bar fill 2 times faster and less enemies spawn.
OR, because that thing would require to edit the whole path, here is an easier method:
If entering alone story path, you have access to a golem like "special force training area" for raid which one can buf you with might, protection and so on....
Pretty plz, I love taking my time and explore everything, and it's better alone, I don't want to be blocked due to mechanics/ enemies.
I don't care, if you consider buffing yourself when you are alone doing story as cheating, remove rewards it's fine, I just want to be able to finish it.
And of course it's not available when your party is 2 and + members.