I`m not good and just got back to the mod but since no one added comment I figured my 2 cents can`t hurt so here goes.
1. Do you have full supply?
2. If so its either tech or unit size (or you have bad tactics). also remember factions have have different types of units like the Reich last i played them (its been a minute) had regular infantry div and were vertically stacked allowing you to make it a larger div than any other faction i played in the mod.
3. Also Reich once they get the stg33 get a little op so it might be your fighting them too late game.