A good tip for the Soviets is to avoid stacking their units that have firepower ratings all in one area. As the game progresses some of the guard units begin to pile up and they can launch some nasty attacks.
However making huge 10+ firepower groups means the Germans will save their ammo shortage or engineer cards to neutralize that attack. Probably better to make a bunch of smaller shots instead.
Not all certainly, but a strong Russian firepower area can be successful. If you can remember (we always play with closed discard decks) how many German cards of either type have gone by you can mitigate the risks. Once had a 14 point Russian area and obliterated four German units that had penetrated an adjacent +3 area - basically halting the offensive on that side of the board.
By the way M. Kurgan seems like a Soviet deathtrap in a way with the +1 cover and abundance of German heavy artillery. I'd pile the 0 units into it - anything better (with a 2 or 3 fp) is gonna get stuka'd and picked off due to the bad cover.
It is a killing ground to be sure. But remember, it's tough to take an area in SoS: one surviving unit maintains possession for the current owner. The longer it is kept the more tactical options the possessor will have in the final stages of the game. And IMHO, this benefit goes a long way to justify great efforts to take or defend it. Another point to consider is that each card the German uses to take MK, will be one less he uses against those tough +3 areas.