Change Astro Vera

I don't think this is necessary. The plant itself is easy to counter, but the boosts are pretty significant. The only frustration I can say that you might experience is when a player has a heartichoke on the board and then plays an Astro Vera to kill you, but that actually is really hard to set up. You have to make sure your heartichoke stays alive till turn 8, draw the astro vera and heartichoke, or have both the cards in your hand at turn 12 and the zombie hero at 10 health with no block meter. 

I recommend putting more heavy cards in your zombie decks (lots of frenzy gargs and tricks) to simply either outperform the plant hero's health boost or beat them down on the higher brain turns.