Since the other thread is only about the good units, I'll chime in on units I've found not worth recruiting.

Toxotai - no explanation needed.

Armenian Skirmisher Cavalry, Armenian Horse Archers - Hayasdan can trivially acquire Scythian HA in level 1 regional MICs (Kotais, etc.), so there's really no point to these units. The Skirmishers are far weaker than the HA, and the Armenian HA are identical to the Scythians with a substantially greater upkeep.

Scythian Axemen - similar stats to all the other axemen in the east, but a smaller unit size.