It's powerful, but I don't know if it's good enough yet. It just takes so long to come out, and most cards that summon or interact with treants are on the slow side as well. And the decks that give you that much time usually won't care if they are 2/2s or 3/3s.
It buffs many other cards indirectly, like The Forest's Aid, Cenarius, Tending Tauren or Garden Gnome, which should not be underestimated. Even Witchwood Apple is significantly better when you get 3 2 mana 3/3s. However, summoning Treants is still a bit too clunky and not quite strong enough. It usually takes too long/too much mana to get the synergies going, making it too slow to stand up against aggressive decks and too weak to grind out control decks.
Still, I think this card has some good potential. Maybe not this expansion yet, but if summoning Treants should get easier some day, or gets easier to include in other deck types, it's quite threatening to have 3/3 tokens for the rest of the game.
this might have been interesting if it did something ridiculous like make your Treants permanent 5/5s but this effect that late in the game is honestly so minor that this basically just seems like an Ancient of War with an orange gem. “For the rest of the game, your Treants are 5/5 Ancients.” would have been a cool callback to Treespeaker.
The deck kinda works right now, but with the pwoer level increase going up across the board, even with these two new treant cards I can't see it working. I've played the decka fair bit, and it's all aobut getting Mulchmunchers to cost nothing or close to nothing - 1 treant for one card won't work, there is no value there, and 1 perma cast of blessing on the ancients isn't good enough, especially as not everyhting you play on to hte board is a treant - you need to run mecharoos and such just to stay in the game and not get blown out early on.