Well ...
It doesnt matter to everyone, except halflings ... they as far as i know (didnt test yet) cannot critticaly miss.
Average chance of a Critical Miss = 1 out of 20, so 5%.
Halfling rerolls 1s *once*, so their average chance of a critical miss = 1out of 20 out of 20, or 1 out of 400, so 0.25%.
So yes, still possible when you consider how many attacks they might end up make. This is why I *hate* it that Larian has decided you sometimes have a 100% chance of hitting a target.