Why did I buy these diamond cards? Because I'm an idiot, that's why. I think I'm going to just sell them. Maybe I'll hold the diamond Skeleton Hoplite because he is actually good in certain decks I enjoy playing like zombie.

Otherwise, it's not worth sacrificing any win % to add shine to your deck.

I ran numbers just like you did and came to similar results. Even multiplying the extra gods x2 for the first three games doesn't justify sacrificing any win %.