The Groovy Cat card for druid looses its buff effect after new hero cards are in place. The card states that for the remainder of the game your hero power will give an extra +1 attack per effect.
The new Artanis hero card looses this buff, despite the hero power doing the same thing as the normal druid hero power, except replaces armor for a divine shield. The card effects should remain in place as it is technically an overall nerf where it cannot benifit from cards such as Free Spirit (which buffs the armor gained) and cannot stack armor anymore.
I would expect to still gain the hero power buffs from the cards played that clearly state for the rest of the game!