On the Shia, they would have been what the game calls an "undercurrent" in this period. It wasn't really until the Safavids that Shiism was a religion of state. I'm still trying to figure out how to represent Shiism properly, and believe me I want to...
Yeah, livestock raid seems to compose a huge amount of the game mode, and to be honest the slow pacing and entire premise of the mode is really dull. Caravan raiding and field battles can damage a kimgdom by a lot, but stealing a half dozen cows from a few isolated peasants doesn't really seem worthy of a gamemode.
What! Cattle raids were epic...http://en.wikipedia.org/wiki/T%C3%A1in_B%C3%B3_C%C3%BAailnge
Okay, that raid was a myth. But the raiding represents a whole series of clashes and skirmishes over months, not just the few cows going back and forth.
On the game, there's a couple of reasons why I want to maintain it. It pulls players to the center of the maps, and it requires some situational awareness. I've had some memorable moments ambushing, getting ambushed, and going to a hill to scan the villages for smoke and riders.
I'd like to improve it, though. One thing it could benefit from is more tension -- ie, you're trying hard to keep cattle ownership above and below a certain threshhold, more all-or-nothing to the scoring, and you have a better sense of the balance of ownership. Other ideas that don't go too far from the basic premise are also very welcome.