I loving the chariots,
you shouldn't use them with sieges of bridges or inside your own line ( will be disrupted)
I ahd a situation inside a city, were a bunche of HA's got trapped between my phanlanx and the charging S chariots. they chose the chariots, the battle was 3 seconds... They may not be a powerfull as elephants, but can be trained everywhere(!), and with 2 HP they are a goog rundown-opponent for HA's
against inf they arrent the best, but disrupting a phalanx form the flank is nice when your got your own phalanx about to fight.
the are also quite capable of kamikaziing, since they can be reatrained in any settlement with a armory(!) so they are a nice canonfodder with extraordenary capabillities.