Key phrase given varying emphasis below, in the spell description.
That means the caster directs it's attacks -- in the least, it should bypass the mirror image (since hte caster will direct it to hit the correct image). Blur is a bit more tricksy, but ... in all honesty, Occams Razor would seem to indicate: if the caster can see X at a certain degree, and the spell is under his or her direct control and direction ... the spell acts as if IT could "see" as well as the caster can.
So, Occams razor says: the Hand whacks as well through Blur, Invisibility, Darkness, and so on, as if it were the Caster's own hand.
Bigby's Clenched Fist
Evocation
Level: Sor/Wiz 8, Strength 8
Components: V, S, F/DF
As Bigby's interposing hand, except it moves and attacks as directed by the character. (The character directs it as a free action.) The floating hand can move up to 60 feet and can attack in the same round.Since this hand is directed by the character, its ability to notice or attack invisible or concealed creatures is no better than the character's.
The hand attacks once per round, and its attack bonus equals the character's level + the character's Intelligence, Wisdom, or Charisma modifier (for a wizard, cleric, or sorcerer, respectively), +11 for the hand's Strength score (33), -1 for being Large. The hand's damage is 1d8+12, and any creature struck must make a Fortitude save (against this spell's save DC) or be stunned for 1 round. A stunned creature can't act and loses any Dexterity bonus to AC. Attackers gain +2 bonuses to attack it.
That means the caster directs it's attacks -- in the least, it should bypass the mirror image (since hte caster will direct it to hit the correct image). Blur is a bit more tricksy, but ... in all honesty, Occams Razor would seem to indicate: if the caster can see X at a certain degree, and the spell is under his or her direct control and direction ... the spell acts as if IT could "see" as well as the caster can.
So, Occams razor says: the Hand whacks as well through Blur, Invisibility, Darkness, and so on, as if it were the Caster's own hand.