Here's my take on this deck, and why:
Mark of Water -- to power Growth and a couple of Water cards.
Emerald Pillar x10 -- Duh.
Sapphire Pillar x2 - to power multiple Growths in a turn.
Forest Spectre x6 - The core beatdown.
Empathic Bond x3 - Over time, even with only a couple of creatures down, Empathic Bond will give you more HP than Heal.
Jade Staff x1 - For creature-resistant decks. Upgrade this first if starting from unupgraded.
Jade Shield x1 - To reduce swarm effectiveness and eliminate direct-damage as a viable threat.
(Alternately, Ice Shield, if you're willing to save up the Water Quanta to cast it, would be better once it actually hit the field.)
Freeze x3 - To reduce single-creature effectiveness, whether its an annoying skill creature like Otyugh or a Crimson Dragon.
That's a deck that's assured to get the core beats out fast, but has the tools necessary to deal with the variety of situations that AI3 can put you in. It would be nice to get some permanent-removal in there, but it's just not an option given these elements
With a little lifegain to deal with the early-game damage, a little damage reduction to survive things like Skeleton swarms, and Freeze to put the inevitable skill/huge creatures on hold while you out-Grow them, this deck should have a 90%+ vs. AI3, easy.