Snip
Your post is incomplete.
If we analyse the design of a faction based on how they were initially conceived or even when they release, you'll find that what you mention on your post has a lot of gaps.
Soviets
You mention 6 man as something iconic but i think
SPAM a single type of unit to reflect reality better, which was caused by unit performance and teching cost.
Reminder that teching was so expensive that you were limited to use only 2 tiers on most games on top of been hard to give up map control to take eons buildings your first tier of choice (hence the old 5 con meta). On top of that, they were so restricted in what they offered that once you picked either of the 2 lower tiers, it was almost guaranteed which of the late tiers you would pick.
T1 was mostly paired with T4 and T2 with T3. Units were on different tiers as well. SU76 was in T4 and T34 on T3. You would either get snipers with Su85s or maxim spam/con spam with T70 rush/T34s.
And i'm not even mentioning doctrinal units. How many years of Guard Motor, IS2s and in teamgames ISu152s.
Semi trash non doctrinal units which only work well when spammed and commander choice holding the faction together made any "weak" commander inviable for years.
Ostheer
Biggest design issue has been: you eventually get access to all tools, but T4 will always be a premium tier which is hard to get in 1v1 but will roflstomp once you get access to it. BTW we didn't think how this applies to teamgames so don't quote us on that (Relic).
PD: if you get your units to vet2 you win. That is, if you can survive the soviet T70 rush and con/maxim/sniper spam and all the shit SU has to wipe your units out of existence.
It took time, but they eventually balance the match up, but it was a shame the design would no be able to hold when they released WFA.
PD2: so call combined arms design was brought to it's knees several times when the meta was gren spam or even pio spam. Teamgames saw also MG42 spam (specially with suppression bulletins).
You can somehow make heavy asymmetrical designs to work, when it's limited to a single match up. Throw more viables and the concepts is thrown away from the board. You can see this with the concept of comeback and factions been strong at different stages of the game. "Wait till i get my CPs and turn this game around with my commander" design.
You hit the head of the nail in the "intermission".
The problem with both WFA (mostly OKW) and UKF is that the initial design would never be able to hold any kind of playtesting. It sounds "exciting" on paper but when people start playing around with it, you see how broken it is, and you found yourself with little to no time before you have to release it and sell it to the public. It's impressive where we are now, despite the disaster each faction release brought to the game. Specially when we consider that the time between beta and release were so close in each case and how faction design has to be completely reworked with little to no play testing.
A few words on each faction.
USF: what you mention basically describes a faction which is design to zerg rush. End the game before the opponent has any chance to react. That's why we got Rifles into M20 - Sherman. This is also the reason USF would roflstomp in 1v1, specially OH, but would be utter shit on 3v3+.
USF got a mortar, because OH got a mp boost and an HMG42 at T0 because they wouldn't be able to hold ground against Rifles/RETs. Diversity was also a reason after we had to nerf the shit out of RET and other alternatives to just spamming Rifles.
OKW: it was basically the forbidden love child from SU and OH. It got all the cheese from soviets, while retaining the powerhouse of late game from OH.
There was basically no way to salvage the initial RELEASE design (to not confuse with beta design). Even if you have so many flaws and weakness early on, turtling and late game carried the faction. Which made them broken for 2v2 and onward for 99% of the playerbase.
This design made it so it was annoying to play it with and against in 1v1, specially in the SU vs OKW match up (clowncar/maxim spam).
UKF: was basically OKW release for allies, but learning SOME of their mistakes they made. They still made horrible decisions with sim city and lacking tools (which were only there in the form of cheese). They had to nerf them for teamgames (specially commanders) but they would initially suck on 1v1 (which then they added clutches as the AEC to make them viable).