My main gripes with Ostheer are:
- 4 man grenadier squads suffer too much from RNG wipes from explosive weapons. It's much easier to get a nice core of vet3 main infantry with the other factions than it is with Ostheer. I think grens should be 5 man squads instead of 4 man squads, with appropriate stat adjustments to make the unit as combat effective as it is now.
- Brumbar is a bad unit. Its accuracy is sub-par and it has no other redeeming qualities. A panzerwerfer is a cheaper and better choice in 99% of gameplay scenarios.
- Prostruppen spam is slightly too effective.
Your point about grens is spot on