If this gave a free trigger on etb, followed by an activation cost of 3, I'd play it in unpowered. As it is, too slow and requires constant filling of the yard.
I really like the idea of having this in hand, opponent plays thoughtseize or equivalent to open a window for them to play a creature, and then choose not to attack into a nearly uncounterable removal.
If you can't follow with a creature the turn after playing this, I feel like this card will not be great, regardless of it's fantastic minus ability. I'm sceptical about this one.
I rarely post, but I enjoy everyone's input. Hermits and Hornet Queen deserve another good answer.