Its imperfect interaction that requires you to have big creatures on the board, and its vulnerable to instant-speed removal or combat tricks
Aetherworks Marvel Energy decks get wild with Aetherworks Marvel
If it was cast by Garruk's controller, he or she can choose which one stays and which one goes to the graveyard.) (Note that as Clone enters the battlefield as a copy of Garruk, it will have 3 loyalty counters, because that's a property of the Garruk card.) It was possible to have Clone remain on the battlefield even under the old rules, but it required a much more contrived set of circumstances
If you really enjoy playing with Starfield Shepherd and want to lean even further into the toolbox direction, this would make a great addition
My favorite option, however, is Ghalta and Mavren, making your army into a giant Dinosaur or a second army of 1/1 Vampires