I am not so sure that it is broken. It comes into play tapped, and does not unbalance the game since it would be restricted to 4 in a deck. I would use it, but I do not see it being a "game breaker". Plus its effect would work for everyone, so that creates a balance all on its own.
The first thing about the card is that i wanted to make it powerful, but go against the idea of most fast green decks.. it comes into play tapped, then next turn if you use it, you still don't get the benefit.
If anything, it's a bit too good. The toughness bonus doesn't do much, although it might help some opponents out. But a land that taps for GG is very good and coming into play tapped, while an obvious drawback, is more than worth it...