Two things that you need to keep in mind. One, it always does 1 dmg + ammount of cards you have in hand, so if you have seven cards it will deal 8 dmg. Two, spell dmg is super good in this, because it doubles the damage done.
Might be better than people think. Handlock turn 3 should have 7-9 cards in hand (and nothing on board), so that's probably an instant clear. The 3 mana cost curves better into your 4-drops than Hellfire (if you're going second, it can still curve into Giants).
Additionally, this card is better depending on the ratio of minions you control vs your opponent controls. If you have one large minion on the board vs 4 smaller minions, each shot will have a 4/5 shot of hitting theirs (that ratio reducing as they die). This card can also go tall if there's just a single minion on the board.
It's also going to be better than Hellfire vs divine shield or reborn. I'm looking at you Khartut or Zilliax!