Just got a critical miss out of a 98% hit chance. Boy does this reminds me of fire emblem
This is actually exactly the same chance as rolling a critical miss on a 51%, 36% or 19% chance. From the probability you can tell that all are advantaged attacks, so you get to roll twice on each and have to take the higher roll. That means if both throws are 1, it's a critical miss on each. http://zerohitpoints.com/Articles/Advantage-in-DnD-5