With Armenia, I never found it much effort to deploy vs. Phalangites

1) HAs in front, they gun down any real cavalry the enemy has
2) Kluddolon mercs en masse in the centre, they suicide charge.
3) one weighted flank of heavy cav. overruns their side (flank while the enemy try to deal with mercs)
4) the other heavy cav. flank the other side if that goes to help.