I can't believe I typed out that much while not making any constructive advice. I apologize for my sleep-deprived state. In general, I suggest 4 things to make this class more generally viable.

1. To avoid having deceptions bait out your main move, I'd have the non-godsblade know foe ability detect (roughly) the number of HD other creatures see relative to its own HD.
2. While I see that you're pressing your failsafe role, not having anything to do for over 2/3 of all encounters is a bit much. I'd modify Godsblade to function for 1 round/encounter and 1/day function for an entire encounter when used instead.
3. To make #2 viable and prevent the party from being wiped out when this is used in case of emergencies, I'd take out the fall unconscious clause altogether and replace it with a lesser penalty like exhaustion.
4. As I'm suggesting that the godsblade use its ability more and with fewer penalties, I suggest removing the "bonus to attack/damage = enemy HD" part of the class feature and replacing it with a flat attack bonus equal to your Con or Cha modifier (whichever you think is more appropriate). The defense-piercing, massive damage and killing blow parts are fine but this one could get very unwieldy as it's the part of the class features that make certain creatures of just about any CR tissue paper for a godsblade.