MP is where they come into their own, cause they are very much a suicide unit, so they are pretty useless for extended campigning.

That said, they can be vitall to the pontics, very cheap and will cut up seleukid and Hai heavy cavalry, when you are still to poor to afford your own. Just make sure to support/sreen them with your own light cav (which you should be able to afford), and use your general to mop up the remaing enemy cav after 30s or so, chariots are useless are killing everyone, one man can kill and entire unit, cause they are so clumsy. (I have actualy seen this happen, belive it or not)