The current VP patch HARSHLY punishes big cities. I had a game where I reached 46

with India by early industrial and was forced to quit. That said, given the style of boost that Etemenanki creates, and given the difficulty you were playing at, 40

doesn't seem that outlandish. We expect the next version of VP to iron-out some issues which are currently making 4UC Babylon unplayable.
I have wanted to try a game with Babylon for myself; perhaps this is my call to action. I played them until Medieval one time, and since the gold generation and

/

in the city are low enough in early game, the wonder seemed fair to me. I did not get to play into Industrial, where empires are amassing 300+

GPT, and the capital is producing 200+

/100+

, but converting ~200

into 30

/20

didn't seem that game-breaking when we first designed it.