Those same expensive sturms are pretty OP in the opening game, if you lose them at start, that's your problem. OKW also has repair drones so...
It is enough to engage them from range and they die like flies. Even cons are a threat to them. If you make them charge You they just die. So yes, they are powerful, but not as powerful if You know how to handle them.
Same as Soviets and USF, CE and Echelons can only sweep. Again, you get one at start, so you're not paying anything. While other units are less expensive, they are also much less combat ready.
It changes completely when you are in mid-lategame. Sturms will probably never really fight and then crews, echelons, sappers and even CEs are just a better option due to their smaller bleed and to being more disposable. Echelons and CEs can do many other things such as sidecapping and supporting pushes, laying mines and sweeping. Echelons will be used as bazooka squads. OKW sturms won't be able to do all these things at the same time - they will become the most expensive repair squad. The discrepancy is actually huge.
Your trucks will get barraged if you put them close to the frontline, again, your problem.
The UKF, for example, will repair their structures more cheaply and bleed less. You don't seem to understand a simple fact that other factions can make the same "mistakes" with much less deadly consequences. That is the balance issue.
You want to put volks with repairing? So, OKW, which has the best tanks in the game and non doctrinal super heavy would also have spammable units early on to fight and later on to repair. Basically you could play aggressively with the tanks knowing that you will have a super fast repair.
Tanks are not the best! That is a myth. The real problem is that tanks such as panther have to be in range of tank destroyers and at guns to inflict any damage as panthers have inferior range. Their healh pool gets depleted very quickly. That is why OKW will need repairs more than allied factions who just outrange axis in general and can deal damage being out of range themselves.
Get a grip with reality achpawel and play some custom games with allies or become better with OKW. Get a grip.
I play all factions and actually that is something U can write to yourself I'm afraid. I find playing allies so much easier. Personal attacks change nothing, just show lack of arguments.