Rostov is easy to defend. But it is also easy to be outflanked.
There are only two rail lines that lead into the Caucaus. One goes through Rostov....the other goes through Stalingrad. But you can attack along the roads in between them to cut Rostov off. And if the rail line to Rostov is cut, its game over Rostov. The units will either retreat, or stay and die out of supply. So what happens is you will put a large army in Rostov that does nothing, but wait to retreat into the caucaus. I think it is better to minimize the units/defenses and try and entice the axis into attacking it. Better they lose 10k infantry taking it early, then nothing taking it later.
I think it is silly to try and build divisions when the front line is screaming for replacements. I mean, you *can* if you want, but how are you going to get them men? You could disband some stuff, I suppose, but at 30 steps of infantry a turn, and losses that at least equal that if not exceed it every turn, it seems rather pointless.
You do, however, get an awful lot of divisions as reinforcements....which can be thought of as "production".
As for the North, I feel (and I play the Germans) that attacking along the North edge is non-productive. The edge works to the defenders advantage, as the Russians can just pile along it as well...and as the russians, would you rather the Germans were fighting to gain Millerowo/Stalingrad/Rostov and threatening the Caucaus? Or fighting over useless territory? Even if the Germans get to Saratov, it will just be a worse Stalingrad, with the Volga protecting its flanks. (FUN fact: There are only TWO bridges over the Volga: Astrakan, and Saratov)...(Another Fun Fact: In winter, the AP cost to cross a river is ZERO)
The Caucaus...hmm...I strongly believe that the Russians should just give up the Caucaus, and retreat down to the mountain passes and River... Supply costs to move through mountain hexes is PROHIBITED, so the Germans need those narrow passes...so plug them up with armies. You only have to keep them out until winter, when all those
rivers cease to exist along the front.
Which should leave most of the actual fighting in the center.
“My logisticians are a humorless lot … they know if my campaign fails, they are the first ones I will slay.” – Alexander the Great