They are OP because they actually have a purpose and you can't find their VERY obvious flaws? Midgame they are garbage. They are only good when you pop them out as a surprise attack. Once they retreat, and have to start going from the front, it's just a manpower waste. I believe it's something like 35 manpower just to reinforce them, which they die very easily, and not counting the manpower to call in. All while you can get a conscript squad for 20 more manpower that have more utility. All I see now is them actually having a chance as a viable commander. If you are a good axis player, you will make them pay for their commander choice. Put mines in front of doors, boom, no more issue. Or build obers,minefields in back, or mg in back, doing so cripples their only use as the commander. PPSH's were trash before, again at least they can do something now. doubling the dmg isn't that big of a deal when it was nothing before.
Don't be obtuse, the squad is only 210 manpower with the damage of STG Obers at close range, and decent damage at mid. They may be squishy but they vet up fast and get molotovs, cloaking, and grenades. You can just camo them on a fuel point and wait for a squad to come up and insta wipe them out of camo at close range. They only need to get one wipe and they pay for themselves. Any they will beat any squad that is alone (except for some vetted infantry) and near a building for only 210 manpower.
They best way to counter partisans is to blob your units so they cannot pick off lone squads, which is not a good influence on the game meta.