I remember calling out to Dave Humpherys, who was at the time the lead developer of the set (Dave, Billy Moreno, and Ben Hayes were each the lead developer for a while Unstable was in development for years)
Amass orcs was created to capture the feel and flavor of a Tolkienesque army of orcs, like the one at the Battle of Helms Deep
For example, if a land that has become a creature dies, an ability that triggers when it dies triggers twice
Other than that, we see UW and Jeskai strategies of various stripes continue to post results in December, while Eldrazi and Taxes and Abzan Company have slid down the rankings slightly since September
And then, at the end, you have a death trigger for 6 damage to someone's face, which can be a bit of a deterrent