OKW has the highest cost tanks in the game with no abilities to boost resources. Panther/200fuel and P4/150fuel. If your opponent has 1 and 3 as you claim then you had been loosing for a long time. Really isn't design problem but a skill problem.
These are also best tanks in game with best scaling in the game. And last but not least, most durable ones.
You need to be that special snowflake to lose late game armor as OKW.
This is why meds and above got +25fu cost on top of what they costed.
Not to mention, combination of that powerful infantry and armor was simply overpowering. 90% W/L ratio have been a good prof of that.