I keep using the checkboard system in the post-reform army, with Legionaries in the first (well, second) line and Praetorians or Urbans in the second, with Auxiliaries at the outmost of the second line.
That makes five Legionary cohorts, four Praetorian/Urban cohorts, four Auxiliaries (due to the expected losses), at least two heavy cavalry and the rest for ranged weapons, mixing Javelins and archers.
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