Hayasdan reforms

[d'Arthez]

In practice yes, namely those that require a higher form of government than unreformed Hayasdan allows for. There are some excellent units that require reforms.

[Stark]

Could you tell me which one? Are they shown here:

https://www.europabarbarorum.com/fac...dan_units.html

[d'Arthez]

Basically all listed high end units.

Going by the EB Recruitment viewer, since I don't have a Hai savegame available to check:

Zrahakir Netadzik (Armenian Armoured Horse-Archers)
Kardakâ Arteshtâr (Persian Hoplites)
Toxotai Syriakoi (Syrian Archers)
Khuveshavagan (which can be found on the Seleukid info page)
Shipri Tukul ( Babylonian Heavy Spearmen)
Mardig Sooseramartik (Armenian Medium Infantry)

And then there is of course the Armenian Elites:
Nakhararakan Aspet (Armenian Noble Cataphracts) (Homeland only)
Nakhararakan Tiknapah (Armenian Noble Infantry) (Homeland Only)
which technically do not require the Persian reforms, just the basic first reforms.