We talking about Finders Keepers again?
The card would be busted at 1 mana no overload. It would be strictly better than any card of its kind (Taunt, Deathrattle, random minion).
Why? Because it Discovers from a much narrower field of cards. And that field consistents of generally good cards. Not all over powered mind you but good to great cards. You only have two duds in Dust Devil and Forked Lightning... and in some cases even Forked Lightning can be good.
Nor every Discover is valued the same. The narrower your pool of good cards the better the Discover is. Shaman overload cards have board clears, direct damage, removals and big bodies... stuff that are good in clutch situations.
This is obviously played in the same deck you play Lava Shock and other overloads. The 1 mana means it's easy to squeeze in between Lava Shock turns and get the refund. I am not saying this card is great, probably not even played but I feel that the card is getting improperly evaluated by having it be compared to Journey from Below and I Know a Guy.