I would link u some of our 4v4 USF clan games(we went 43-4 in 4v4 before northweapon quit
and show you, its very possible to win 4v4 early game as ALL usf, especially vs okw. really only ostheer stands a chance and its because thye have suppression
Really the keys are
Never send in a squad alone, evne in the first engagement. Wait till ur riflemen is with your RE to push with both of them. Sturms beat your RE? stop sending the RE by itself. Sturm and kubel beat your rifle+re? Wait for your second rifle, sturm kubel and volk? Wait for your 3rd. A forward HQ is suicide for OKW, if you need me to explain why i can.
Ambulance after 3rd, maybe 4th rifle for constant forward presence, soft retreat when you get down to 2-3 rifleman models. this allows you to heal up and basically out blob volks simply because of a high hitpoint pool+ damage output as the early game engagements roll on, they cant soft retreat as well as you can. ambulance heals better than anything in the game. Abuse the hell out of that.
Basically you want to keep regerenating your riflemans health, while wearing down volks and sturms with constant bite, and retreat assaults instead of full assaults with full retreats, or single half hearted assautls against a combined force.
Coordination with your teammates, as well, you need it as allies. of course if u have No coordination any faction is invincible.
tldr
attack with multiple squads, always fight an engagement where you're outnumbering. never send in one at a time, send in 2-3, when one squad gets low pull them back and just keep up a constant assault, coordinate with your team, etc.
And also, even if they nab the fuel and things dont go well to start despite all that, relax. Just have a General Macarthur "Ill be back" attitude, youll be fine