Equality policy is fine. I pick it last by default because I don't need more happiness before that time. In the long term it does its job. In this game with the Celts you don't need to pick this policy at that time. If you want to make it more viable as a third policy it would need to give something else on top of happiness. From my experience happiness is not a problem at that stage of the game. I think it's up to the player to use his brain to figure that out. I don't pick Equality as a fifth policy for the happiness, but for the gold per citizen birth and the ability to build the Forbidden Palace.