Here are my thoughts, for future reference.
5) Soviet decks:
Soviet Armor Reinforcements are too far away and/or too expensive.
In my game, I drew only one card from the soviet armor reinforcement deck and took a KV-1 (cost 5) on turn 2. Virtually unplayable, since with the "deep snow" slowdown, it would have moved 3 (advance) or 1 (fire and move).
I've seen other armor reinforcement cards cost 9 (2x T-34); that type of reinforcement couldn't enter before turn 4 and I don't think it would have much of a chance of aiding the advance or reaching the final escape point.
For this reason, after the first card I immediately stopped drawing from that deck.
I tried drawing a couple of cards from the Soviet Reinforcements deck, but I got two identical cards: two squads of regulars with the GMC truck option. Given the presence of deep snow and the difficulty of the forests and tank traps, I thought it would be better to call the units alone (without trucks). Their movement would still be limited to three open hexes and only two hexes (if one of them was forest). They were too slow, and if they entered after the third turn, they wouldn't have had a chance to reach the exit.
At this point, I drew exclusively from the Winter deck, which, however, was shared and therefore ran out too early.
6) Soviet units:
The Soviet MG and mortar are fairly useless and fall far behind, almost too far to have any impact on the endgame.
Perhaps replacing the MG with an SMG could help?
7) Soviet specializations / Soviet operation cards:
The Soviets have only one engineer unit (no more can be added from reinforcement decks). I've always found the "clear tank traps" operation card ineffective. The engineer must already be on the hex (having arrived there in the previous turn) and be completely exhausted to remove the tank trap. This requires at least two turns, hoping not to suffer any opportunity fire. Combined with the fact that T-34s are much more mobile and agile, the engineer's role has been largely ignored.
As you can see from the replay, the Soviet tanks used the "upper corridor" to bypass the traps in the lower part.
Final push
When the Tiger tanks appeared, they stopped exactly on the "R" hexes to form a "wall" against the approaching Soviets.
Six Soviet tanks (one of which was heavily damaged) managed to enter the forests and, with a couple of combined fire actions (and a lot of luck), they managed to eliminate the German tank ace.
This created a corridor that allowed two Soviet tanks to exit, and on the following turn, an infantry unit to do the same.
The other two Soviet tanks that attempted to pass near the Tigers were wiped out by some amazing dice rolls.