I agree with Xenogeist. I can't see anyone putting this in their deck in its current state. Since it's common, and since manually discarding cards doesn't happen that often, it's the kind of card that's likely to just pile up in your hand and take up space.
Another problem is that (except in a specific case like vulture), when an opponent does discard a card, it's probably not a good one (I'd guess the most common manually discarded cards are searing flames and purified ashes).
Maybe if it had some secondary effect?