Groot is a really beefy ally (there is one of only three for aspects in the game, that had 6 hit points.) Potentially our Big Friendly Tree can block infinity times, but in reality in expert mode this will be good for 2-3 blocks (and small attack/thwart in beetween last defend) which is insanely good.
Obvious trait locked make him not playable in everydeck. But still this is A (auto-include in all Guardians deck), and now with the player side schemes he can be defend even for others heroes.