I remember the meta where control warriors would play Archivist Elysiana and then bounce it so they could add 20 cards instead of 10 to their deck for the mirror. It was nerfed to 9 mana to prevent this so that it wouldn’t drag out games too long.
Now? We have Kiljaden, which unconditionally adds an infinite # of cards to your deck (granted, with a maximum of 30 at a time) and makes the cards more powerful every turn. This is really the issue here. Drawing through your deck super fast in itself isn’t problematic because the penalty for that is if you run out of value you hit fatigue and get grinded out. Getting rid of the punishment for decking out makes hyper draw decks just pure upside with no downside.