I mean, besides potential silliness you can do with knife juggler with the scheme upgraded, i can see that. Besides that, other then in grim rally/spirit of the bat style zoo decks...the card very....ehhh.
This card probably needed to start at 3 1/1 imps to be worth considering.
Then this would make it unfair in comparison to the other schemes like Hagatha's one (5 mana deal 1 damage to all minions). The shaman spell needs at least 2 ticks, in order to become good (when it deals 2 damage, it's like a Volcanic Potion; @ 3 - Excavated Evil).
Or it's cost needed to be 1 or 2 mana.
However if it cost 2, it would have been better I agree.
Think about the unstable evolution synergy you have after you get that spell from cauldron though. Wait what? Unstable is being rotated out. Okay stormbringer synergy lmao. Devs that dont actually play games are useless.