One more proposal so far for the route from Russia through Kazakhstan.
It depends on where you're going to enter Kazakhstan:
If you want to go through Astrakhan city (Russia), then:
a) You can go to Atyrau, Aktubinsk, Kustanay, Astana, Karaganda, Alma-Ata and then to China. Quite a good road (Astana - Alma-Ata even excellent).
or you can take another one
b) Atyrau, Aktobe, Aralsk, KzylOrda, Chimkent, Almaty - this south route is somewhat worse than the first one. Some parts of the route even can not be called 'a road' at all.
If you go into Kazakhstan through Orenburg (Troitsk) city (Russia), then:
Enter Kazakhstan via Kustanay and then move towards Astana.
If through Chelyabinsk (Russia), then:
Enter via Kurgan (Petuhovo), Petropavlovsk, Kokchetav, Astana and then Almaty.
If though Omsk (Russia), then:
Enter via Pavlodar, [Astana, Alma-Ata] or [Ust-Kaman, through east part of Kazakhstan to Alma-Ata]. Not so good roads.
Also you can take a look at the route of the Evan McGregor & Charlie Burmen from the "Long Way Round" (route images.
There are still no roads in the area of Atyrau-Aralsk-and further along the route shown.
P.S. Sorry if I misspelled any name :)