I'm not particularly happy with the new war script, for a variety of reasons.
1) The AIs are far too willing to go to war, even with fast friends. In my current game, I'm playing an OCC with the Kuriotates on Monarch. I founded Runes and have been in the religion the whole game, spreading it to Varn and Mahala. Varn eventually summoned Basium, who converted to Runes too. Now, you think this would be enough to keep them from attacking me? No. Keelyn (who founded the Ashen Veil and the Octopus Overlords) declared on me, and I was already at war with Hyborem, and shortly after this, Varn/Basium declared on me, followed by Mahala also declaring war on me. Mahala I can understand, since he's supposed to be an opportunistic bastard, but Varn/Basium should not have declared war on me, their faithful co-religious Good ally from the beginning of the game, while ignoring Keelyn and Hyborem.
2) The dogpile functionality, in general, is bad for the game, IMO. I feel like I'm playing Civ2 again, where the AIs would all gang up on the human player. I didn't play much before patch f, but it seems to me the threshold for declaring war is too low: AIs should go to war only when they think there's something to gain, much like human players. I'd prefer a method of encouraging people to build defenders via a less gamey mechanism, if that's what the dogpile's goal is.
3) Despite declaring war more often, the AIs aren't any better at waging it. Their biggest problem is they just don't build enough units, and they don't collect the units they do build into attacking stacks. I've fought with Mahala, Keelyn, Basium/Varn, and Hyborem, and I've yet to see more than a few pillagers enter my lands. In unmodded civ, I usually play with BetterAI, so I'm used to its dagger strategy: a good human can still beat its stacks, but it requires more units and better tactics. While the details of FFH2's combat system are a lot different, it seems to me that the general outlines of the dagger strategy are still applicable: build lots of units, group them in large stacks, and avoid pillaging with all but a small fraction of units. Might it be possible to introduce this to FFH2? (I'm a novice programmer, and I'm not very familiar with C++, so I'm afraid I can't easily answer this question myself.)