Yes. The chance to divert attacks is based directly on your Ninjitsu skill. The formula is skill -30. So at 120 Ninjitsu you have a 90% chance that an incoming melee attack will that WOULD have landed (not Parried, or missed due to DCI) will divert to the Mirror Image (for this reason, similar to Counter Attack, it's better not to have DCI). When this happens the monster loses target on you, you keep target on them, the monster will retarget you quicker if any delayed damage then hits them such as Bleed/Poison ticks, Hit Spell/Area etc.