I have to disagree on the stalingrad battle tactics.This is a common misconception.Russia did use raw human wave tactics in the first days of stalingrad ,after chuikov took command however he made some very imp modifications.
Human wave attacks were cancelled.Instead best troops were divided into small assault groups armed exclusively with SMGs They would do mobile fighting,and present small targets for german air and artillery strikes.The general infantry was mostly used to grind down the german advance from garrisoned houses and the devastated urban terrain.These houses acted as strongpoints holding down the german advance cauysing huge casualities in close quarters brutal fighting.Some the famous buildings used a s strongpoints were the tractor/tank factory,the granary,pavlov's house.The soviet troops were ordered to take up positions so close to the german lines that the luftwaffe would be unable to disntinguish between opponents and unable to bring its firepower into play with full effectiveness.
Among the barren devastated landscape between the ruined buildings,assault parties from both sides roamed the city.In this no man's land chuikov unleashed his sniper army.His famous directive -
''Every german soldier must be made to feel that he lives under the muzzle of a soviet gun''
And nor did soviets pour everything they had into stalingrad.They poured just enough to keep the fight for the city going,acting as a sponge absorbing german strength.While the real soviet buildup continued on the flanks which would culminate in operation uranus.
Can't deny there are separate action with Small Unit Tactic action involved but generally the overall course of Soviet Campaign in Stalingrad is the use of sheer number to repulse the German attacks.
While as you mentioned, some objective the Russian seized it with small assault group but the question is, if you repeatedly send in small assault group to attack a single objective, then you are still using human wave tactics. (Which is exactly what Vietcong did to the US in Vietnam war) Which you would see most objective the Russian counter attacked has been using this repeat method to engage and destroy the German troop in the surrounding area.
While German follow a combined force tactics, which is to engage the enemy weak point and high point in effect to use their artillery and tank, then separate pocket to the remaining urban fighting. The Russian have no unified objective on how to retake the city. The battle rage on wherever the Soviet Reinforcement got off the Volga and they fought then and there. While the ground troop on the front line attack and defend objective regardless of their strategic and tactical value.
In Urban warfare, we are train to prioritize building by their use, function and their location, a force fighting with combine arms tactics would engage the building with the highest tactical value according to the war plan. For example, if there are 4 building in front of you, and if I have to attack and occupied 1 enemy building so that I can get better defensive support, I would occupied the highest most building both serve as vantage point and serve as observation post. The same goes as to defending the city. However, not much can be seen in Stalingrad, beside the tractor factory and the assorted railway station and yard, defensive line are hold whenever and wherever the friendly troop was.
Conventional military wisdom suggested that the Defender will enjoy a 3:1 ratio of troop uses before weighting in Air and Ground support. However, as you can see the situation, While the German suffer 800,000 casualty in an offensive, the Russian lost 1.3-1.5 mil (Approximately 2 times) with the defender. Which usually would be the other way around.
The only reason Russian did not buckled during this battle is simply because they have more strategic reserve down the road
and the distance to replace the lost troop is no where near as far as the Germany has to replace them. On average, a single lost Russian troop can be replaced by another within 24 hours in battle. While the German side have to take 2-3 days. This is also a serious contributing factor on how Russia win the war.
Had The location change and this battle is fought nearer to Germany, the outcome could be a lot different.