Chariots are great for disrupting enemy formations, but as stated, they need to be kept moving. One great way to cause chaos is to have lots of chariots go straight through the middle of an army line or two, and then have your troops running along behind to quickly fill the gap created by the chariots.

This splits the main force in two AND gets your chariots behind the enemy, and in a really good position to harass and cause more havoc (or deal with pesky cavalry). Force your infantry to widen the gap you've created, and at that point, units will begin to rout. I've done this before but it requires timing and a great opportunity (like really light infantry units and missile units positioned in the middle of an army both on the front and rear lines). It worked well enough in Vanilla Rome when I was dealing with the Romans as the Bretons, though whether the same concept can work in EB, I'll have to see. Custom battle time!

TL;DR: Keep Chariots moving or they lose.