Certainly nobody would normally recognize that his Totem is smaller...Hiwa complains that my Totem is bigger than his
This is the most likely scenario, IMO. Yet most of us will buy the expansion and will love it despite all the muddle. We are suckers for this game.The diplomacy is already a muddle. If you add two complicating factors (religion and espionage) without improving it, it will become an even bigger muddle. The backstabbing doesn't bother me; aggressiveness doesn't either. It is just too many AI diplomatic actions (including DOWs) are blindingly stupid and self-destructive; they bother me even though they often work in my favor.
I'm not just talking about how the AI treats me; they can't even tell who their major AI enemies are, and they squabble with each other while that enemy swallows them up. Adding more factors without fixing the basics would be a big fail.
Civ5s issue with diplomacy is lack of variety. In the late game, there's not a lot to do other than to constantly scheme against each other. Gods and Kings might improve that by adding city states into the mix, as they will no longer just be a gold dump. There's also been various suggested improvements to the UN that they will hopefully look at.
As for Civ5 AI and how people perceive it, I already talked about it in length here just recently. The AI isn't broken in the sense that it's not working. It's working as intended. But if you come in with expectations of being able to bully, bribe and cajole AI into submissively sititng in their corner while you take over the world, go back to playing Civ4.
When I'm interacting with civilizations, I want to feel as if I'm interacting with a leader, not with a computer.
To what end? The only goal that a "leader" should have is to win or at least prevent the human player from winning by whatever means necessary. The weakness of the AI is that it does not know how to finish games effectively, allowing a human player that is way behind to get a cheesy win. (Or allow the human player to get way ahead because some feel they should step aside through diplomacy ). The only purpose of having AI opponents is not give the human player a sandbox game but to agressively remove you from the game.
I can imagine two scenarios: Let's say Hiwa and I both start in forest area and both adopt "forest" religions. Maybe you can build religion specific wonders, like the shrines in Civ IV. Assume you build it.
a) The way the AI is acting now would mean that Hiwa complains that my Totem is bigger than his, and DoWs me. I would consider that a fail.
b) Or the AI would recognize your common religion. Maybe you get shared bonuses from the existence of the hypothetical shrine. It would encourage mutual existence. If religion leads to a more reliable AI, that would be great.
I guess there is a wide range in how leaders will react to religion. Kind of like the difference between Isabell and Victoria in Civ IV. I am fine with that, since it would mean that religion does not dominate everything, but would mean that overall AI allies are more trustworthy.