Maybe the Beast Tag comes into play? Seems kind of underwhelming otherwise. Battlecry won't trigger with Hadronox.
A 4/8 for 5 with taunt that comes back with Hadronox (even as a 2/6) is definitely good.
Also not sure the upgraded Druid Hero power is worth it.
I think it definitely is. All the 2 damage hero powers (Mage, Rogue, Druid) are pretty much worth it just because 2 damage beats so many popular 1 and 2 cost drops. And it loses value after turn 7 or 8 or so, so it's definitely still worth running Malfurion anyway.
I don't see this as viable without substantial investment into the new expansion. There is no benefit to odd/even mechanics in previous sets, and several important cards like Spreading Plague have to be abandoned. Unless you already got Baku, I would not build my deck around this odd mana cost mechanic.