I feel that we (or is it just me ?) might be somewhat blinded by the way we've been playing 4X games so far, where we impersonate a single culture/civilization all the way through the entire game.

To me, based on Amplitude Studios' proposal for the game and the gameplay mechanics revealed so far, the ability to switch from one culture to another in each new era, is actually a very interesting and smart answer to this imbalance/overpowering concern in most of 4X games.

I hope that, if we have the chance to play an early version of the game, we'll be able to test those multiple combinations between cultures (at least some of them), and see how they affect the balance of the game. I actually think that it will highly promote a "situational gameplay" : we'll have the chance, 6 times during an entire game, to assess and weigh the opportunity/necessity to switch from one culture to another.

And even in the case where we decide to "transcend" our culture (from the beginning to the end, or at one particular point in the game), it has been said that we'll have some "Fame" bonuses (I believe higher than any other opponent who is not following this transcendantal path) that will help us make it through to the end of the game, and potentially ending up winning.

So I think balancing all the cultures/civilizations, making them even, would actually be counterproductive with regards to this switching ability the game is proposing. But I certainly agree that it would also be quite frustrating if, after having played a certain amount of time, you find yourself playing again and again the same pattern of cultures/civilizations to win.

I hope (and I think that Amplitude Studios made it pretty clear) that we'll have a lot of combination possibilities so we can fully enjoy these different cultures/civilizations, and a new strategy each time we play the game.

PS : this thread and this thread are also very interesting with regards to imbalance/overpowering.

There will always be imbalance if they allow this type of historical game with choices. Dont fool yourself that there will be balance. The only strategy game that managed a very good balance approximation between more than two civs is SC2. 

I am sure at some point a min maxer will find a culture sequence that will very much strong destroy while others are just mediocre.