I used Yue Ying to finish all of the Chaos scenarios. She can be very helpful because not only does she have a bow, but she also has a "Special Start" tile in her skill tree, which means she'll also start with a tome. This may sound like nothing, but in any level where you run in to kill a general, this can definitely make or break you.
Any weapon with Flash makes your life about ten times easier, not joking. With Sun Shang Xiang as an example, I was able to last a lot longer in Chaos with a power 79 weapon with flash than a power 91 weapon without it. This was before I went to using Yue Ying for every level.
If you've got an excellent horse (eyes consider the world, heavenly physique), then you'll have a huge advantage since you can run, preserve renbu, and recharge musou if necessary. Musou is crucial when fighting generals on Chaos, it's basically the only way you're going to inflict serious damage. I happen to have one (it's named Valiant Cloud, and it's of the Dapple variety with Winged Hoof, Renbu Gait, Musou Spirit, and Arrow Dance), and I don't think I would have made it through Chaos without it.