I don't see this card seeing much play. It suffers a lot of the dormant problems of other cards in the past, with similar revival conditions, like the one card (don't remember it's name) that revives when you cast four spells in one turn. Now if it revived after five turns, minus one turn if a friendly minion died (example - five start, minion died revives four, two die revives in three turns) or revives after five minions die. It could see more play but might cost one mana more.
I think you mean that plant. From Rogue. Sherazin or something like that...? Actually did see some play IIRC, I remember playing it at least. With those Flowerpetal 1 Mana deal 1 dmg things. Sortof Rapid Fire.
But that had actually a lot of natural synergy built in the deck for it, it's just what Rogue does. Now with Hunter, he also summons a lòt of stuff, from Hyenas to just other cheap-ass 1-drops and cheap beasts. But I think the literal single fact that the Trampling Rhino is such a huge thing in Hunter rn, is what's gonna be a huge, huge hurdle for our boy The Rat King to overcome.
I hope he manages to do so, maybe with a small nerf for the former, or rather a bit of a different statline for this one, maybe 6 Mana 6/6, or 5 Mana 7/4 or something like that. Will be interesting to see what Blizz will reveal for other synergies apart from the 6 Mana Rat Infestation already, only time will tell.