It is hard for the viewer to find any sympathy for the main characters in the first half of the picture as the enemy hasn't been clearly defined. If the terrorist ISIS style tactics of the "Turks" had been clearly shown at the start of the film then the cast of "Cossacks" would have had the sympathy of the audience from the start.
Once the audience knows what kind of brutal savages the Cossacks are dealing with the film becomes much better. In the first half of the film Nils Asther appears to be the more attractive choice for Renée Adorée as he is more handsome, cultured and civilized in comparison to John Gilbert (especially as Gilbert treats her poorly, at one point even striking her). Once Nils Asther is out of the way, however, and the barbaric actions of the Turks is made known to the audience, it is easy to empathize with the characters.
The film would have been much better if the horrific barbaric nature of the Turks had been clear from the start. Otherwise it appears that the Cossacks and Turks are just bands of crazy violent people who attack each-other for no good reason.
Needless to say the modern score is terrible and anachronistic. I watched the film on mute and play a period Synchronized Musical Score (from the 1929 film "The Single Standard") and it fit nicely with the mood of the film.