I don’t think winrate has anything to do with how viable a faction is. In every multiplayer game the most used faction/character is usually the strongest and/or easiest to play.
People like to win, and thus flock to the strongest and most forgiving thing. And unsurprisingly the top 3 most played factions are Sov, OKW and Werh. Brits/USF being lesser played factions is not without reason.
I agree with most of what you but it's really Sov and Wehr, with the totals always looking skewed because one side has two factions and the other has three. There can only ever be an equal amount of multiplayer games for each side so the one with three is going to look wildly fucked up and the one with two doesn't have any other choice.
Sov and wehr being the most solid factions in terms of dealing with shit thrown at them imo makes the positions at the top pretty reasonable