And half the time, Wager will give your opponent 6. Wager and Admin also force you to shuffle your own hand -- disrupting your opponent when you know his hand is good isn't always worth disrupting yourself.
Looker reveals your opponent's hand and then allows you to make a very strategic choice -- either force him to redraw, or redraw yourself and proceed while now knowing your opponent's hand. Making your opponent shuffle is huge if that key card is already in their hand. Even if they redraw some supporter to get to it, you've forced them to burn their supporter on that next turn, which wasn't necessarily their plan. It's disruptive, plain and simple.
I really don't see the negatives you seem to be hunting for.
You forced them to burn a supporter as you yourself have burned your supporter use on Looker. Nullifying the effect.
5 cards is too many.
Nothing we have will ever compare to Admin's disruptive ability. Wager is still more disruptive than this card. At least there's a fifty percent option of giving them 3 cards (which will actually hurt if you're power locking- unlike 5) or to give them 6 is barely worse than giving them 5.
Negatives:
1. Only hurts opponent when they have a god hand. Any other time it probably doesn't really affect it or it improves it.
2. The redraw of 5 for yourself isn't as good as Cynthia's for 8, or guaranteed 4 no matter what.
3. Giving your opponent a new hand of 5 is only slightly disruptive. If you plan to power lock, giving a new hand of 5 is often enough for them to bypass the lock.
I'll almost always want to play Cynthia in a deck over Looker. There are a few decks that really benefit from him, though.
Going off of Chin's comment:
If you have a bad hand and they have a god hand, who do you give the redraw?
So you enter gambling situations when your opponent and your hand ratings are severely different, which happens often. You also can't get the benefit of double redraw, like if you have claydol out and also want to disrupt. Wager is so good for this, because if you lose you still get to draw a virtually new hand of 8-9 easily. And worst case the opponent gets a new six, but you still got a lot of new cards to see.
There are a lot of times when Looker will be really bad.