[@CrystalApple]Guile and Subterfuge shouldn't give an effect like Mind's Eye. Emiya, a counter guardian and extremely talented assassin himself, only has the skill available at B. While it comes with the handicap that they must be observed Assassin is purposely not going into a fight. While it is debateable if a skill like that should be part of a multi-subset skill then it should be at D, or C-.

As for the noble phantasm what does it do exactly? You have a great amount of detail but it doesn't exactly spell out what it does. More over I'm not comfortable with the notion of changing someone's legend. From what I'm looking at it it basically hand cuffs any servant that isn't divine, or Saber/Lancer/Rider which all three can be undone by simply managing to get close to, or using it on their master.