No faction is stronger by default. If we went from the reverse situation then it means there is a point in-between where better balance lies.
Its not the strength of the faction, its the adaptability of the factions. 3 factions are forced to spam mainline, they are predictable, they are redable and most importanly they dont have answers to many of EFA oppenings\mid game units.
Hell, say you have a chose alright. You have USF and you have Sov.
As USF you know, that you have to controll your rifles perfectly, you know that on paper you are stronger but in reality its not always possible to get in close\mid range fights, you know that your success depends on either you being a better player or your oppenent screwing up.
As soviets, even if you went with the wrong strat, you always can do a flip and get something which will help, if not win, but at least make enemy snowballing much slower. Same with Ost. And the most importand as ost\soviets you can also win by being a weaker player, simply because you managed to outsmart your opponent by bringing something he dont have answer to, unlike WFA factions.
To put it much simply, WFA factions just requare perfect play most of the time to get the most of them. And considering really small amount of variety and the fact that their mainlines are usually overburned with tasks in early\mid game, they are being pushied for a mistakes much more.
As DevM said about OKW vs USF match up. On paper USF should be stronger then OKW in early game, but in practice you just cant get into situations when USF gimmics will kick in, thats the problem.
This is territory close to "faction revamps", which is pointless at this point. Balance team cant buff OKW\USF\UKF in this situation. Because it would either be such a small changes no-one but top players will even recognize or they could buff them overall but we will retern to pre-nerf WFA armies.
Top players play with ost\sov. Automatch is unbalanced crap opponents wise and stats wise. So why even bother at this point? At least outside the tournaments all 5 factions are somewhat playable, good page to end CoH2 history on.