I voted for this card but i got some problems with it i want to point out:
The upped version costs one more and only gets one more damage. The damage reduction increases too but the effect of the first point reduction is way stronger than the second one because of fire shield etc, some 1 damage things and the survivability of all nukes (i mean it survives one lightning/shockwave because of that one reduction). I dont think that increased cost isn't justified.
The other thing is the ability Snake Bite. Why should a giant turtle have a life leeching attack? The main purpose of that ability is the damage because usually creatures are on full health (especially Genbu with his immunity to one plague, fire shield etc.), so i recommend to remove the life draining and make it a simple "Bite" ability.
Overall Genbu is too cheap because it's a 7/5 unit with effectively 6 hp minimum (+ability) and only costs 6, usually units have much less hp (Ghost of the past, dragons) and that cost level.