Reading a few articles about WW2's Eastern Front, it seems to me that the Soviets always seemed to suffer huge casualties during battles with the Germans. Even during their victorious battles in the later stages of the war, the ratio of casualties never seemed to be in the favor of the Soviets.
Why did this occur? Were Soviet tactics inferior, or were their troops more poorly trained?
Short answer is, in Siuvet Union (and nowadays in modern CIS countries) the value of human life was (and still is) much lower. Here is a quote to describe the common tactic:
Highly illuminating to me was his description of the Russian method of attacking through minefields. The German minefields, covered by defensive fire, were tactical obstacles that caused us many casualties and delays. It was out laborious business to break through them, even though our technicians invented every conceivable kind of mechanical appliance to destroy mines safely. Marshal Zhukov gave me a matter-of-fact statement of his practice, which was roughtly 'There are two kinds of mines; one is the personnel mine and the other is the vehicular mine. When we come to a minefield our infantry attacks exactly as if it were not there. The losses we get from personnel mines we consider only equal to those we would have gotten from machine guns and artillery if the Germans had chosen to defend that particular area with strong bodies of troops instead of with minefields. The attacking infantry does not set off the vehicular mines, so after they have penetrated to the far side of the field they form a bridgehead, after which the engineers come up and dig out channels through which our vehicles can go. (Eisenhower; Crusade in Europe, John Hopkins University, 1997)
Here is a short journal paper I had saved in my bookmarks regarding the actual number of Soviet casualties. Its only a few pages and addresses the commonly touted 26 million casualty figure and breaks down the different causes of the actual military deaths. That being said, it does not address your question about potentially inferior tactics/training, and I very much hope someone will address these issues!
Let me start by saying that I am in no way an expert on WW2 history, or any history for that matter. Simply a high school student that enjoys learning about history, but I'll give it my best shot.
After Lenin died there was a power struggle between Stalin and Trotsky, Stalin got his power from the bureaucracy while Trotsky got his from the military. After Stalin came to power he decided to purge a large part of the Soviet military to get rid of Trotsky's supporters; unfortunately this also caused the Soviet military to lose most of it's experience soldiers and commanders. When war broke out on the eastern front of WW2 the very well trained, equipped, and experienced German army was met with a lot of new recruits, led by a bunch of inexperienced generals.
The Russians also have a long history of being a little bit behind the Western and Central European powers in terms of military technology, but they can make up for that with their huge population base and command economy allowing them to shift their production to military hardware easier than most other nations at the time.
TLDR: They had lots of inexperienced soldiers, and less advanced technology.
P.S. Feel free to correct me on anything I got wrong.