hariots pose the same problem to your units as your knights to your opponent's units.
The additional attack on the charge is less valuable than the higher save of the knights. So the points value of chariots being less than that of knights is ok. On small battles (less than 2k) they proof to be more effective, not because they are better than in a large battle, but because the first close combat might decide and end the battle, so that there is no time for a counter move.
So what to do about them ?
A lot of the things said about securing flanks is true for countering chariots. These are the 3 main approaches:
- Kill/Cripple them from a distance
- Charge them before they charge you
- Get charged and kill them as a retribution.
Kill them from a distance:
Try to concentrate your fire on them. If the chariots are not the closest target, magic is a good way to "shoot" at them nonetheless. Also restricting your own fire arc is a valuable tactic. Often you can turn a unit in a way that a close enemy unit will move out of the firing arc making an enemy unit that is farther away the closes visible target. Sometimes it is also a good idea to sacrifice a unit by charging it into an unit that would otherwise be the closest target for shooting. Even if you can loose only some shots at the chariots, you might get a lucky salvo and destroy a stand or drive them back and/or confuse them, which gives your troops time to close in. Even if you only cripple the enemy unit this is highly valuable, if you can stay out of initiative range as his command roll will be modified for the stands lost. You can exploit this further by positioning a unit close enough to add another 1 to his command roll.
Charge them before they charge you:
Sounds simple, but it isnt most of the time. Your cavalry is as fast as his chariots and are able to pursue, so they are first choice for doing so. With everything being equal the lucky one will charge. So you can try to tip the luck your side. One thing is to make sure that you will pass the command check for your charge move. The Orb of Majesty is quite handy for that. Also the "Voice of Command" spell is of help especially when combined with the Ring of Magic.
If you do the charge with infantry, try to charge from the flank (for cavalry also the preferable direction, but not as essential as for infantry) and have a second unit right on the opposite side. This unit does not have to take part in the combat but must be close enough to block any way of retreat for the chariots. Whatever you do be prepared to fail a morale check and if possible stay out of initiative range (only possible with cavalry) until the charge goes through.
Get charged and kill them as a retribution:
In the plans below there is always some sacrificial unit placed about 15 cm in front of the retribution units, which can be anything good enough to kill the chariots on the attack.
You could place a Knights unit (if there is only 1 chariot unit charging) to take the charge of the chariots. Statistically only one chariot stand would be left after the combat and that can easily be countercharged, but the points balance wouldnt be good.
The other way is to have a double line of infantry, crossbows to the front and halberds in the back. This double line should be positioned far enough ahead, so that the chariots have no other valid target (like always). The advantage of the double line is that it can take the charge of 2 chariot units. The crossbows will die and the chariots will have to advance into the halberds (they are closest) and cant charge anything else. The points balance if charged by one unit is a little better than with a Knights unit, but you will not loose an offensive element of your army.
Build your defensive line in a way so that he will have to charge your artillery as well. I.e. a unit of crossbows backed up by halberds and an Hellblaster at the flank. When charged by more than one chariot unit, you will have 9 stand and shoot shots plus 9 ordinary attacks. These are enough for killing 2 stands with a 5+ save.
I do not mention explicitly the obvious things like placing infantry in defended positions and the like.