You dont even need it on the battlefield
On top of that, the fact that it exiles and returns your creature when it leaves play makes it ideal for blink shenanigans
Shorikai, Genesis Engine While cards like The Belligerent and The Indomitable can be your commander as of EOE, Shorikai, Genesis Engine has the distinction of being the first legendary vehicle that could be your commander, at least on its front face (hi, Cosima)
But all other versions of this Phyrexian dragon (including Secret Lairs) are well below $20, so I doubt $59 will be a realistic number post-release
While The Valeyard doesn't do much on its own, it's a means to an end to leave your opponents weak for the rest of your deck to close out the game with burn and combat damage
This could also let Simic do it without having to be RUG, but the problem there is neither of these creatures have trample, and you can remove the Ox with a single mana white spell, soooo