From the currently seen standard deathrattles hunter has access to, i don't see this seeing play, but in wild this will probably make it into so many decks, 3 mana take control of a random enemy minion and add sylvanas to your hand? Yes please
This makes me think so much about Necromechanic. If you can play her and play this card, you can get their Deathrattle twice (which I hope that interaction does work) and that's done before your opponent can take care of the Necromechanic. As for wild, there are much more powerful (and/or broken) interactions with card.
Great concept and I am glad this card is coming in after rotation.
There is no strong 1/2 mana deathrattle minions you want to trigger with this one. The only decent early minion is Spider Bomb, which will make it like a Deadly Shot with a card draw, which is very good. Of course it can trigger heavier deathrattle from heavier minions, but that comes much later in the game and you don't want for this card to be a dead card for numerous turns, if it's in your hand on turn 3, you want to play it and get value out of it, and that's the problem, there is no good 1/2 mana deathrattles you want to trigger it with.
So this card is quite slow and inconsistent atm, maybe that will change with introduction of new cards.