Got my Great War freikorps last year and the casting was fine.
You can use Copplestone turks with headswaps for more variation w officers. Mix them with white russians for Latvia maybe..
The first two packs of Brigade's Austrians were done by Mark Sims of Crusader and are quite similar in style to copplestone. Mixed with russians they'd make perfect POWs, or Hungarian reds.
The Brigade Germans are fine too. Sizewise similar to the early BoB packs. I have the light ki and stormtroopers mixed for my freikorps.