Don´t build the T-34. Don´t build the SU-85.
Take a T-34/85 doctrine. Later try to mass multiple T-34/85s.
Another viable thing is using the lend lease doc and Spam M4 Shermans without teching.
Go for short engagements on different parts of the map. Try to kill infantry squads and stay mobile. If you don´t, you will get defeated by a Pak wall or a Schreck blob. The art to master Soviet tanks is to only go for short engagements, before the enemy can concentrate his AT weapons on your tank. Shoot and scoot. The biggest weakness of this however is Teller-mine spam.
I prefer going for a doctrine that offers viable mediums + the conscript repair kit (lend lease + advanced warfare). This comes in handy if you like conscript spam.
t34 85 or m4c sherman aint that necessary at all.
su 85 is really viable vs panthers specially when with vet i rather have some t34 85 against me then vetted su85's these tanks are real beasts! the only thing is getting them vetted...
t34 spam can also work but you must make sure that you get a lot of them 3 to 4 atleast but it is never enough (rather 6). a way to get a lot of t34 (and more importantly keeping them alive) is the renewed sovjet industries commander. you can call in a lot of fuel drops you get like 30 fuel each time (is almost a half t34) and with some decent map control you should be able to get alot of them. you can keep them alive with crew repair and repairstations. so you dont have to spam engi's . to seal the deal you can also add in a kv2 as meatshield while your horde of terror is flanking around