I don't know about German bow as I'm a French player, but I'm sure what I'm about to say applies to both:
- Even on the shortest notes, there must be some arm movement. The wrist/hand alone cannot generate a good sound without the weight of the arm.
- How short are these notes you're talking about that you're only using 1/3 of the bow? For an allegro tempo 8ths should get at least half a bow, and at a slow tempo a whole bow. Quarters almost always a whole bow.
This is again only for the "default" stroke. There's obviously a lot of other options when you get into articulations, spiccato plus you might want a certain effect like bowing slower near the bridge, etc. The above advice would be for developing a solid orchestral stroke to which adjustments can be made for the other techniques.