Worst Case Scenario: You only have forests and green mana. You get a 3/3 Vigilance Trample for 4. I’d be happy to play something like that in limited.
Probable Case Scenario: You have green mana and one other color. A 4/4 that can play defense and can’t be chump blocked is a fine bargain for 4 mana. But I’m still not disappointed, and that’s very aggressive. The only trouble is that it doesn’t trade with Siege Rhino, and that might turn out to be a big deal.
Intended Scenario: You have all 3 of your deck’s main colors, but no splash 4th. As a 5/5 with those two abilities, we’re looking better than, or at least “on par but different than” Siege Rhino, the gold standard for tri-color 4-drops.
Outside Shot Scenario: You have your dedicated 4th splash color, too. This is obviously very good value. 6/6s with Trample and other such abilities tend to come with drawbacks, like “you can’t win the game” (Abyssal Persecutor). If you some how manage to miracle this on the third turn, you’re looking like a winner.
Magical Pixie Land Scenario: You have access to 4 colors for mana and Hardened Scales. 7/7 Trample Vigilance on turn 3. Game-breaking if it survives. Yet surprisingly, it doesn’t feel like a lot has to go right to make this happen.
A lot of this is going to depend on cards like Rattleclaw Mystic, which can really power up your multicolor madness. Likewise for Hardened Scales, which is an auto-include in decks that play this tree-beast and his other elemental friends. In my mind, I am evaluating this card based on the probability that he’ll enter play at any given size.
As detailed above, the most likely situation yields a powerful card that might still be below “replacement level”. We can take 2 colors of mana for granted when casting a green 4-drop, so we’ll consider this creature a base 4/4, with strong chances of being better. A 5/5 for 4 mana is very strong, and it seems like with the right supporting cast, easily attainable.
Beyond this point, the card needs no further discussion, as the potential to max out at 7/7 with the precisely correct draw exists and is obviously way above power level.
The only drawback is that it dies to removal. There, I said it. The good news is that the best removal for this is probably going to cost at least 3 mana, and at sorcery speed. I imagine the deck that wants to play this is also going to be playing Undergrowth Champion, which will do its part in trying to eat removal as well. Some of your creatures will die, and that’s okay, because each of your monsters are enough to end the game outright if left unchecked.
Ultimately, I like this card because he can present a really under-costed threat without much, if any, additional effort in strategy or deck building. It’s a blunt force instrument, not an asset to be grown and protected like the aforementioned Champ. If it eats removal, fine. If it doesn’t, it will dominate the board without a doubt. The combination of Trample and Vigilance means that you’re in command of the combat step.
I’m seeing current pre-order prices in the 3 dollar range, which seems justified for a card that’s obviously constructed playable.