MF was ~55% hp, and jhin shot his 4th shot, 30 mins into the game, running 100% crit, I'd assume Jhin would have around ~500 AD with a crit, that damage makes perfect sense from Jhin.
MF with dark harvest with her score, I'd assume around 180-200 stacks + 75 base damage at level 16 + ~55 from the ad items alone, since she auto'd with storm razor it guarenteed a 200% crit, she also has upfront damage from duskblade and rapidfire cannon, if she Q'd initial Q actually doesn't crit ever, do I think the damage is justified? With her build yes, but should it even be allowed, so if she Q'd, it'd actually deal slightly less damage well no, but the entire reason she could do that in the first place is duskblade and taking a scaling rune that is dark harvest, You take those 2 out of the equation, running a normal crit build would probably make her hit that jhin for about 40% for the initial hit if it critted and around 25-30% per additional crit