The thing about sturms/IS is that they are very positional units. Tommies who aren't in cover at the right moment will get chewed up by pioneers who manage to close the distance before the tommies can get in position. Spios caught at range will take serious losses closing the distance and if there's any negative cover between you and them they will just lose.
Pioneers are seriously good against UKF early game if you engage properly. Sniper + pioneer buddy makes it really tough for individual IS to accomplish much.
I do like that fighting these units has a bit of nuance, personally. I think tommy reinforce should really go back up though.
you're right, and that basically comes down to player attention and micro but spios/IS will still beat RET/CE/pio the vast majority of the time and will win hard if the victory conditions favour them. given that teams are
rush the important building maneuvering with has almost nothing to do with the first 30 seconds. after that it opens up but by that point RETs/CEs/pios are preforming some sort of utility or indirect fighting role (rifle nades/flamers, mines, demos/sight). an HMG and a pio is also at a pretty big disadvantage against 2 IS or an IS and a vickers and will flat out win if they get the building first. additionally, USSR/OKH is at an even further disadvantage if they decide to build t1 as that's longer their unit is off the field.
i guess what i'm trying to say is that i don't have any design issues with these units after the initial rush because the unit counts get closer to equal and these units can do other things but there is a tremendous imbalance for that initial rush (which has little to no place in 1v1s but a huge effect in team games) and it's a design imbalance.