It was not so much the 'grip of the Junker class'; by 1910, this had already been very much diluted, the vast majority of officers - and general staff officers - being 'middle class', although the generality - by nature: old men and very old men - still was filled with scions of the nobility, or by 'middle class' soldiers nobilised for their meritous service.
The issue was one of educating the 'middle class' to the values of the Prussian (err... German) Army, this could only happen in a slow, very slow way in order to make sure they were not diluted by a mass surge of materialistic bourgeois. (The technical branches - artillery, engineers and their offsprings - were already dominated by materialistic bourgeois, nevertheless.)
This was also the case for the NCOs. Even more than with officers, NCOs were recruited from one single stratum of the German society only.
The struggle was fought inside the German Army between the 'modernisers' (e.g.: Ludendorff, von der Goltz, von Bernhardi) who wanted a mass army, coûte que coûte, and the 'traditionalists' (e.g.: von Einem, von Heeringen, von Falkenhayn - the Ministers of War) who preferred quality and a slow expansion over quantity.
It was no social struggle affecting German society. Followers of the SPD would qualify as NCOs at best.