You know, I've never fought a full-strength successor army as the Greeks/Koinon Hellenon. I've always booted Makedonia out of Greece before they could start fielding pezhetairoi, etc. And the Seleukids never send the good troops my way, they're always tied up with the Ptolemies in the south.

Your hoplites should engage the phalanx line head on, then use your Peltastai, Theurophoroi or Thorakitai to flank and chop 'em up. I'd suggest going a little heavier on the Theurophoroi; you'll need them to defeat enemy cav, which has a tendancy to try to flank you.

The successors' hetairoi bodyguard is some of the heaviest cavalry in the game; don't go up against them with just your KH family member's bodyguards. They'll bust your ass up. A detachment of Theurophoroi or two should handle them. Or at least tie 'em up long enough for you to take a unit of hoplites out of Phalans, and haul ass over to the action...

On, and don't understimate the slingers. Always bring slingers.

Back to the Ptolemies, it seems they can no longer recruit Liby-Phoenician Heavy Infantry as of .74. Oh well. I haven't progressed far yet in .74, so I have no idea what else has changed. Sometimes the slightest change can affect how a campaign turns out.