I love it from now on, definately exciting times,
It happened to me once (with only 7 civs though). Shaka was at the head of the Apostolic palace... It was definitely exciting! I almost felt like a shot of adrenaline went through my vein. My first thought: "oh god! I'm in deep sh**!!!"
It's one of the rare times I passed in "total war mode" (Police state, vassalage, theocracy, every possible hammer I could grab spent into military units and the science meter down to make some $ to upgrade every unit I could).
The nice twist for me, it was an archipelago map with high seas. So that made for awesome naval warfare. Movements and strategic positioning become really important in such total naval warfare
At first, I thought I was dead. I fortunately prevailed because very few enemy troops were actually able to land near my cities. I also had the best navy, so that made things easier than I expected early on. I even turned it into a war of conquest at Tokugawa's expense (closest neighbor) Still, it was a rewarding victory.
If I had been able to use the blitz promotion for my ships as described in the upcoming patch, it would have been even more easy.
In the end, I think that maybe Religious crusades are not as powerful as they could be. I mean, most civs (except Shaka) didn't seem to enthusiastic about the war. Even with AggAI turned on, they didn't seem to be that prepared for a war and many civs (Hatchepsut, Mansa Musa and Cyrus) didn't send as many troops as I expected toward my islands.
Maybe it's the naval component or maybe it is the relatively peaceful nature of these leaders, I don't know...
Still, for a religious war, they didn't seem that passionate and "extremist" about it. A reluctant crusade on their part