As I've said in the titanpad chat this is what I think:

: Murderer of the misty night as a skill is ok
12:03 Vance: a free first strike is fine in itself
12:04 Vance: Likewise the mist is ok (as a noble phantasm)
12:04 Vance: it's a debuffer noble phantasm at best, and hurts enemy masters. It
12:05 Vance: It also lets her set up her ability to use her presence concealment.
12:09 Vance: Fighting in the day is all down to luck but remember this is a team based war. Saber, or Lancer can easily make up for anything if they're nearby