I LOVE the mechanic and the creativity, but honestly if you've got 2 9/9s on the board you're probably winning anyway. And with the hard removal that exists out there, a 30/30 might be worse than two 9/9s a good portion of the time.
Feugen and Stallag were similar cards - good stats on their own, but even better when working together. However, to make this guy work you will need a lot of board control - and then you should have already won the game. And if you enemy has a Shadow Word: Death, you just paid 18 mana in order to get destroyed.