I thought the original idea was fine enough, but should work against Fog Shield, as well.
Yes, the card would be useless for a Rainbow deck, but it's a nice thing to have for a mono-Light deck, maybe.
The sad fact of the matter is: half the cards that already exist are "useless," if you define "useful" as "optimal." As pointed out many times, if you're not using Sundials or Hourglasses to boost your draw count, you're crazy to hold more than 30-35 cards in your deck if you want it to be optimal, and this doesn't leave room for flavor cards that may or may not be useful. Hell, shields in general are useless for mono decks, because a mono deck has no way to protect it once it's out (except for earth, obviously).
Here's a better/more useful idea, though: Let the "Clear Vision" effect let you see what cards your opponent is holding in his hand. Since light apparently deals with God-like abilities, omniscience really isn't out of theme.