This is one of the reasons why I adore playing Pontos (putting aside the diplomatic prowess of the AI, but forced diplomacy can sort that out). You can get a diverse mix of units in a small area (that all work well together) and I think the EB team have done a great job of reflecting the fusion between Hellenic, Persian and various local troops.
Satalexton is right about the dilutuing of troops, the biggest offenders being either Romans prior to the Marian reforms or when expanding east from Hellas as Makedonia or Epirus, trying to recreate the empire of Alexander. But this only adds a extra layer of fun and accuracy to the game.
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