Most units scale by either getting good veterancy bonuses (like Puma) or gaining utility (like T-70/222 scouting). Likewise a vet 3 StuG for example still has a decent chance to deal damage to an IS-2 due to the various combat bonuses that it gets through veterancy.
That's different from being able to just spam cheap units and avoid teching up to counter an enemy's high tech/unit cost late game unit just by sheer frontal DPM, which would become possible if deflection damage were to be introduced on a large scale.
Scalability of units should come from either vet 3(/5) combat performance or (veteran) utility. Not from stock performance.
Yeah and this is why some factions can litteraly flat fall on their asses if at some point they lose vetted unit.
What about Mediums? Why one call-in unit (which for soviets is awaible just by teching, since you will get T4 no matter what) should be immunte to two mediums? Why Churchills and KV-2 should be almost immune to mediums, dispite costing almost the same. Why PIVJ should be almost immune to mediums. If you get 2 medium tanks, you've pretty much spend as much res as the guy getting this 1 heavy tank, yet you cant do anything.
And even more on this topic, dont you think that getting IS-2 if enemy is spamming StuGs (in a world with defection damage) is just a bad play? Its like saying, well KT is the most espensive super-heavy in the game, why it can be countered by doulble TD units. Or pretty much any heavy tank can be forced away or significantly damaged even by 1 TD unit, dispite it costing more.
I mean, you for some reason only forcus on the cheapest units dealing damage to the most expensive ones, but at the same time completly skipping the midle ground, where not so much cheaper units cant deal with slitghly more expensive ones, just because they are out of their league.