And ur also forgetting USF can afford double bazooka rifles to support,each have their advantages.
Mark vehicle is doctrinal.Is mark vehicle even available with an is-2 doctrine that u can combo?In t-34/85 doctrine,no one gets su-85 but waits for call-in then uses mark target with that.
What u don't understand is that u can turn away and su-85 won't be able to follow due to about mobility,if flanked its dead.Jackson can not only track ur flank by turret rotation,also demolish u while backtracking unless pathfinding is terrible.Jackson can also chase down wounded vehicles(not talking abt okw blob) which su-85 just can't.
Focus sight is often a weakness for su-85 because of its terrible mobility and inability to turn in time its cone.No my example is that pershing plus jackson would be far more terrifying than is-2 plus su-85 which is intimidating enough.
So your ignoring the facts and putting in scenarios. Simple as that. The SU85 CAN kill armor better and especially with Mark Vehicle. Whether or not that is the meta is not relevant. There has been units with Turrets that did 240 Damage a shot since the game has been introduced. This means the ONLY thing that is special about the Jackson AT ALL is its mobility. Which is balanced by its terrible HPs and Armor.
I can AS the Soviets do better with Dual T34/85s out of Guards Motor then I can with a Jackson. Then I have a combined 1600HPs doing 240 a shot at closer ranges and getting better Penetration as a result AND having AI.
The 240 damage a shot at least in 1v1 where YOU CANT POSSIBLY have Mark Vehicle (as USF) is just a Straw Man.
Especially when you consider there is no IS2 or ISU152 or hell even KV1 for USF.
You can try all you want and throw in all this "What-Ifs" but the stats do not lie. All the Soviets need to do is snare a tank and the SU85 will do better then the Jackson. And Soviets do not lack snares. Now most people wont do that in the current meta because the Teching costs are fucked. That has nothing to do with the units.
Edit: And sorry Double Zook rifles now that is hilarious. You must be talking about 4v4 there...