User blog comment:JoAlter/Minamoto no Atsuko/@comment-32398851-20190319111001/@comment-25310270-20190319173958

I think when DW make plan on creating new servants, they have a range parameters on which a servants rarity has to be in for balancing purpose, and this fan made one, just broke that rule many times over.

The game is a 3 servant teamwork, not about one overworked girl taking over everyone's Job. A servant NEEDS weakness.