Dependence on local units?

[V.T. Marvin]

And as bactria I fought with local peasants only... damn hard

You mean these guys?

Kofyaren-i Kavakaza (Baktrian Light Infantry)

IMHO they are definitely one of those "surprisingly good" units - large size (200 on Huge), lot of javelins and AP axes make them extremely valuable flankers and shock troops rather than "mere skirmishers". They are certainly one of my most favourite units!

Nevertheless, I would complement them with any large-shield spearmen (even something as bare as pantodapoi) in guard mode to form a line to stop advancing phalanxes etc.