It turns out that Garruk loves his beasts more than he loves himself, we just need to put one or more creatures threatening his 6/6 beast and enjoy the show.
The AI throughout DotP is frequently unwilling to trade creatures. Even if it's a 2-for-1 or 3-for-1 block that causes the trade, the AI is often unwilling to try it.
Two Score, Minus Two or: A Stargate Tail
(Image by totallynotabrony)