The Shadow Lord Gix, Yawgmoth Praetor was a pretty strong mythic in The Brothers War, and it should play out fairly similar here
[2] You can target 1 face-up card your opponent controls and 1 Level 8 or higher DARK Pyro monster in your GY
Crop Rotation, Deadly Rollick, Culling the Weak, Diabolic Intent, Phyrexian Altar, Ashnod's Altar, and Phyrexian Tower all play a big role in how the deck takes shape, creating several loops where creatures are sacrificed for benefits like infinite ETBs, death triggers, mana, and so on
In a game where you can already get three prize cards from knocking out a Mega Pokemon, having a card like Iron Hands ex around that adds an additional prize to that could be something of a problem, so its probably for the best that card rotates out
In 1994, when Wizards of the Coast decided to create sanctioned tournament play, the Power 9 were restricted in the very first Banned & Restricted announcement