Honestly I blanked out and assumed the proposed enchantment drew a card when I posted that.
However, you're wrong, I think; at least historically speaking. Disrupting scepter is one mana less on both cost and activation. I'm not sure which is more powerful; denying the draw certainly wins out for aggro, which is where this would go. This brings up another issue, though; I don't think there is a historical precedent for denying a draw, but there is for discarding a card, which this is similar to, but it's in black. Perhaps UB?
My recommendation:
<Name>

Enchantment
Any time a source you control deals damage to an opponent, you may prevent any amount of that damage. For each point of damage prevented this way, add a Weight counter to this.
Remove 4 Weight counters from this: The next time target player would draw a card, instead he or she puts that card into his or her graveyard.
Remove 2 Weight counters from this: Target permanent does not untap during its controller's next untap step.
The name of the counters (Weight) is only temporary. I'm happy as long is it's not charge or divinity or poison counters. Also, there's really a lot of ways this card to go; maybe remove 3 to tap or untap target permanent, or perhaps some clause to allow instants to be played, or something.
It still doesn't seem that great to me. Would it be too good at

?