My difficulties against sov is:
Shocks > smoke VS Mg42
Normal inf > oura + molotov + ppsh VS grenadiers and MG42
Snipers... ( some games they are 6 snipers on the map ...)
They force me to use lot of MP trying to counter thoose units, so i let them a lot of time, areas, ressources to produce tanks...
Shocks have zero anti-vehicle ability. Flame HT destroys them and is great for forward re-enforcing and defense later in the game. Pgrens can also reasonably stand up to shocks, especially once they start to get vet. A sniper can cause a lot of MP drain killing shocks and their vet1 ability is murder on them. I've seen it kill up to 3 men out of a full health shock squad.
Molotovs are easily dodged by all infantry. The AI can be a bit stupid (jumping back into the flames) but looking out for grenade abilities is something players on both sides need to perfect.
PPSH conscripts have the constitution of a sick 6 year old girl. They die quickly to just about any unit that looks their way even at trip vet. They cost the same as grens, so if they're making a lot of cons you can fight them with grens and a couple upgraded grens (either G43 or LMG) will cause a ton of casualties to those cons as they try to rush you.
Don't overlook the mortar. The ost mortar can be a heat seeking missile. Sadly, it's one of the best sniper counters I've seen especially if there are multiple snipers in an area. Most of the time the snipers will get one to two shots off before the mortar hits close enough to outright kill them or cause enough damage to force them off.
If you're playing elite, don't completely skip vetting some units. Vet makes a huge difference and early vet can be a deciding factor. Also Vet 2 or 3 P4's are fantastic and can help delay the need for panthers depending on how the game is going. They also have decent anti-infantry ability.
Also don't be afraid to use MG bunkers. They can be a pain for soviets to deal with early if strategically placed. You can use them to deny a key point, or defensively to help protect an area and some of your set up units like the mortar. Guards in a scout car will make quick work of one if it's left alone, but most other early game units take a while to take one down.
I play 2v2 pretty much exclusively these days so that's where my experience is coming from. 1v1 is a bit different but it sounds like you're playing with a partner anyhow.