That's not how standard deviation works. If we had factions being on the top 5% on certain modes and on bottom on other modes, I'll agree with you. But after 3 months seeing the same factions on top on each mode shows different things.
Fact is that the win rates can jump vastly between different months and even between related game modes such as 3v3 and 4v4. I agree that standard deviation is no indicator of balance being good or bad at all. But people here claim that some factions are clearly UP because of their win rate being lower than another faction's by a couple of percent, while next month or in the next game mode the difference is much smaller or even reversed. This is a strong hint that the data we have is not robust in the first place.
My point is that we have to consider much, much more than just the win rates that the site gives us. We cannot solve the balance issue on the current "hard" data alone. Like it or not, we have to make a ton of "educated guesses", and that's exactly what the balance team is supposed to do. The win rate data can help, but I get the impression that too many people assume it should be the main or even the only metric for balance. Given the quality of the data, this is quite naive.
Especially if we consider that the data is highly interdependent in team games. One bad faction will drag their Allied faction(s) down in the win rate. Some of the win differences can literally be a good team suddenly having two free weekends. Again, those win rates are a hint that something might be off, but definitely overblown in the discussions here.
Few game are decided by early game in teamgame, what decides the game are late game units able to crutch on the opponent and we've seen the balance team working on downgrading Allied late game options while keeping Axis one intact.
It wouldn't surprise me to see the gap increasing once the new patch kick on.
I think this has mostly to do with USF and especially UKF having so many holes in the line up compared to Axis factions that picking doctrines is not a nice addition, but essential to the faction. Allies have 2/3 of their factions hampered by this, while both Axis factions unlock all "basic" tools in a normal teching path (OKW having some quirks but still).
Overall the patch still goes into the right direction in my eyes, but as with every patch we have to check which changes do not work. Overall the patch should not be seen as a general faction balance patch, since fixing the factions via commanders will create more issues once core units get changes later down the line. Previous patches have fallen short on more fundamental changes to mostly UKF, but I'd attribute this more to Relic than the balance team.
Off note, I am quite happy though that team games are finally discussed for general balance. It actually shows us how far the game has come that the biggest issues have moved from easier to analyze 1v1s to chaotic large modes.