I understand your idea, but you have to think how bad this card will be.At least the Griffin needs some form of setup and can just be a reset/ heatwave target.
I liked an idea previously mentioned here, and would like to make Viy closer to the lore, a rampaging insect without control.
I woud lower it's starting strength to something like 4-5 and change it's ability to: " At the end of your turn consume a random unit, then move to the opponent side. " or something similar. Then you could add : " Adrenaline x, lock itself" or " Strength x: Lock itself" .
I mean, we already have wererat wich does almost the same, and its better since its not random and you can setup it.
So you can say, okay, just down the provision cost of viy.
Right, that would fix the card, but will struggle the balance. While every other faction has gain one card with 10 + provision in the WOW expansion, monster doenst have that card. (the way you describe the "new" ability i cant see costing more than 10 provision that card).
So if the devs will change the card, they need to change to something really good and not that crap - with all the respect - you mentioned