I tried taking haomavarga with my combined baktrian army at the start. It had 7 horsearcher/lancer units in there. My battle plan was to skirmish as much as I could with them with my 4-5 units of archers, while under archer cover my two pantodapoi phalanxes came up and blocked the main street while the cavalry charged straight into it and got routed when my cavalry came in from the other side of the enemy mass.

I was so wrong. The horse archers beat my archers by weight of fire and mobility, then resisted my phalanx bait, then mowed down my phalanxes when I got impatient and got them to advance (hence putting them out of phalanx), then turned around and smashed my generals whom I sent in to try and turn the tide. They're nasty.