As with everything you need to learn the weakness of each commander to know how to counter them. That said, playing against the right combination of commanders in teamgames can really be difficult. As Hmortier said, I think the luftwaffe commander is more of a trouble than elite troops when in the hands of compentent players.
KV-8 is totally fine, doesnt come out all that early and can more or less only deal with infantry. As stated above, if any later more expensive or other nerfs, it wouldnt see much action.
Have done really long splines with no error like this. However, if I "add to end" alot on a spline, I end up with a similar bug where the spline seems to break and go backward on itself. I guess its not the same issue you got though.
@OP While your 1st suggestion isnt all that bad (2nd more inf vs inf combat, and something that has been asked for as well. 3rd, I think makes little sense), I think a more proper way to get rid of this problem would be to get rid of the homing nades/fausts. I hate it when I got a vehicle half a screen away that still gets hit by the nade/faust. If you move out of throwing-range, the animation should cancel. This would lead to more kiting of infantry, and less retreats. It would also be harder to pull of that infantry vs tank rush, because you have to work hard to get into and more importantly stay in range while throwing. This means you have to be closer to the tank when you throw to begin with. Why do I think this is the better solution? Just because it only addesses the vehicle-infantry combat and more or less is contained to the nade/faust. This change would give the 221/222 or the m3 a bigger place in the game since they can more easy get out of range because of their speed (might have to deal with more clowncars again though).
The unit needs to be more accessible to all tiers of players, rather than being useless for the majority and extremely useful for "kite-masters," hence small armor or hp buff would be better than some kind of weapons upgrade.
This, especially since all car units (222, m3, katyusha) are quite hard to micro at times when the terrain or objects work against you.
Bug has been around for a while. Doesnt happen very often, but does happen occasionally. Experienced it myself and seen it in livestreams. Have got no replays to send relic tho.
Its quite ok even in teamgames. Since it can take a punishement it is a unit that can "tank". Draw alot of fire that otherwise would go into more "valuable" units. Thats how we use it, when we do (which tbh isnt all that often). To screen and soak damage for other units. Use it wisely and it can help support an attack.