Ooh, very interesting. Lots of attack reducers have been suggested before, but yours looks very balanced. Not too powerful, but not too strong either.
I'm kind of hoping to give Life a mild form of creature control
Thorn Shield?
Anyways, I like it. I don't think the upgraded ability is necessary; I'd just keep the first Gore the same as the second, but increase the Deadly Minotaur's attack to 7 and its casting cost to 5

.
Good cards.