I don't know, 4-6 man squads never were a problem for me, cos they have really pretty same survivability. 2 additional man not always can save your unit. Of course it is annyoing to see, that UK's mortar mine wipes entire your squad or Katyusha's barrage, but for me it happens rare and game is pretty forginving even to Ostheers - 1 or even 2 men in squad usually survives after that. Insta wipe means only bad luck.
For example, I played once as OKW and I got QF 25 shell right into my retreated to FHQ blob. Directly in them. But no squad wipes - each squad just lost 2-4 men, I moved them asaide and reinforced. So, here is very strange system in game, I don't understand it. But, It always trying to save you squads from insta-wiping, no matter how much people there in squad, so +2 or -2 here is not that important. Maybe I understand it wrong, but that's what I saw.
But, 6 man squads can be actually insta-wiped too with Werfer or Stuka or, CAS bombing run or CAS Dive Bomb...
I don't know, what great tools you mean in USSR. Mines are maybe great, but they are not uniqe for USSR, OKW have same mines for very strange reasons. USSR really doesn't have something specific good in stock or even in doctrines. I can only say that stock Katyusha is badass, but that's all... Katyusha is good, SU-76 is more or less good, Guards would be good, if they would be T1 unit, instead of Penals. All others - worse than their analogs in other factions.
And yea - best artillery in game with ML-20 and B-4. But... no B-4 is piece of shit.
Strange that your game experience differs so greatly from mine. Grens, Panzergrenadiers and Pios get wiped by mines, Soviet heavy mortar, ZIS barrage, ISU, IS2 shell and so on. Frequently btw.
On the other hand killing a soviet maxim or mortar is a pain, really. They're so durable.
Fine, unique tools for Soviets: Shocks, heavy mortar, maxim, bombard ability on tank destroyers and anti tank guns, T 70 which is awesome against infantry and can take a punch (though not a big one), partisans (spawning from buildings, cloak, panzerschreck and mines! Hell what an awsome combination!), radio intercept, very versatile Cons (though with bad scaling but still with a lot of uses), etc.! Really there are some great replays and casts out there where you can see the many possibilities Soviets offer. They really have a lot of great tools!