I simultaneously love and hate the way the soviet macro game is played, and I think that any attempt to balance the su85 needs to take this into account instead of merely tweaking stats.
The Good:
Different planned soviet builds are possible using call-ins and certain buildings (or none at all), as opposed to the Ostheer who will have little choice but to make the same units every game to stay competitive, and you will almost never see tier4 in a close 1v1.
The Bad:
Skipping buildings (tiers) + easy economic management for the soviets means the su85 pops out as mentioned right when a p4 does, if not before.
Su85s dont dominate german armor so much as prevent them from being worthwhile to use. As soon as a couple su85s sit behind the soviet front lines in a relatively close game, the ability to use vehicles is almost negated for the ostheer. God help you if you're trying to retake the vps on pripyat winter. It essentially takes an elefant to drive the su85s off to give yourself room to push, but if you have been building armor in a 1v1 you probably wont have 260 fuel to spare at that point.
What I'd like to see is something like this -
Step 1:
Buff t34/76s to make them viable vs panzer 4s statwise, reduce the effectiveness of ram
Nerf t70s so they arent quite the rape machine they are now; speed, armor, dps, choose 2
Discuss: Move su-76 to tier3? then require tier3 building to get to tier4
Tier 3 will take on the role of german tier 3 as the standard mid-game tier, with t-34s as the generalist tank like a panzer 4. I would be very interested to see the cost of t-70s increased as they negate ostheer t2 vehicles and don't have an effective counter other than mines (not a hard counter btw) if you bait them right... then they rebuild it. Ram spam would also have to be adjusted, possibly removing the 100% main gun damage on rammed vehicles. Requiring vet1 for ram would also be an interesting tradeoff.
Step 2:
Increase the time and cost to get to tier4 for the soviet player. Tier4 should be the exception not the rule. This tier4 bullshit at 10 minutes is fail design. Tier 3 should be the main mid-game tier for both sides because it'll be equally viable for both sides (aka buff t34s). Requiring t3 building to get to soviet t4 is a good start. T3 units for the soviet should be worth using, and their usefulness is what will delay tier4.
I think the easiest fix for the su-85 itself is to either cut the cancer and remove the spotting ability, and/or keep it and require it to deploy to fire long range. Possibly decrease rotation speed or accuracy up close since it has a casemate turret and shouldnt be able to match a tank in close combat. Discuss: possible small cost increase
Food for thought--if germans had panthers out at the same time as soviet t3, theyd be calling bullshit. If conscripts are supposed to rape a flanked machine gun, why shouldnt a flanking p4 at 5 meters rape a su85?
i dislike the t3 into t4 purely for the sheer ammount of resoruces it takes to get both buildings, 90 fuel each would give the germans a huuuge advantage in the teching war hows much does it take to tech from p4 to panthers and build hte building? 50 fuel or something around there.
I like the concept but you would need to change the costs of the tiers to make this viable.