Interestingly, I am writing a message about How do I know I'm hearing God's voice right now, and I'm using this exact scripture as a part of it.
My thoughts:
1) Clearly Gideon is unsure of himself (I am the least of the least), and by extension unsure if he is hearing God's voice. God speaks to all of us, but it is a learning process to recognize His voice.
2) Gideon asks these things and says, "then I shall know that You will save Israel by my hand, as You have said" or in other words, then I will know I am hearing clearly. This is not divination in the evil sense, this is confirmation for someone new to God's voice by using what was available.
3) Notice, there was nothing of value gained by the exchange other than the confirmation itself. [Evil] Divination is obtaining supernatural knowledge (from a source outside of God) for personal gain, not the case here.
I think asking for a fleece is a sign of immaturity, but not a bad thing as long as it is done with sincere motives as demonstrated here.