Well I don't think there was any set tactic. Rember, cataphracts were all equipped diffrently. But once an army tried to chase the horse archers, they would end up being exausted. Then the horsearchers could wheel around as the cataphracts charged.
In addition, the amount of cataphracts varied battle to battle.
Also, most infantry lines (especially the non Greek ones) would end up breaking before the charge of the cataphract, out of fear. Or they would end up getting close together to try and withstand it, which would allow the horse archers excellent targets while the cataphracts wouldn't actually charge.
They would also likely be able to win in a fight if they charged other cavalry, but if they had to chase them, then they would fail. That's what the horse archers and the other light cavalry was for.

Likely the Selecuids failure came from their lack of light cavalry. Without horse archers to soften up infantry or chase off other light cavalry, cataphracts would be vuneralbe, and while they wouldn't suck, they would likely end up dying. It's just a guess, however.