I really don't get Genesis Hydra here. The curve of the deck is pretty high and the Hydra itself will always be a below the curve beater.
Because it's a 2 for 1. Nothing gets me back from a bad position like Genesis Hydra. It also synergizes with Courser of Kruphix extraordinarily well. If I see a Banishing Light, I can grab it with the hydra and get an extra 3/3 out of the deal that I can buff with Sorin and Ajani. It means I can dig for a planeswalker on an empty board and still protect it. I can grab a Siege Rhino and get instant value. That kind of scaling card advantage is just massive. Even just having extra shuffle effects is great. Being able to drop an uncounterable planeswalker is insane.
I used to have 3 Hydras and a Liliana just so I could chain them together.
If you recognize that Wingmate Roc is a good card, then you have to know that Genesis Hydra is just better. Hell, I almost put in the Rocs for value with the Hydra but it's too conditional.
It's the glue that keeps my deck together and the pseudo-tutor makes me more comfortable with only having a couple of each of the cards on top of my curve.
No card in my deck has tested better than the Hydra. The Hydra is why I lose to mono green as a control player. It's the 3rd best green card after courser and elvish mystic.