Profile of thedarkarmadillo

And yet you’re only level 4 as OKW. Doesn’t seem that easy.

If the axis are constantly rolling out medium tank 8 minutes in for him I doubt any faction is terribly easy for him. That's the kinda of player that easy bots were made specifically for

Luchs shots bounce off t34 rear armor

Luchs isnt supposed to counter a t34... Try with a puma and report back.

Imma weigh in here and say the brumbar itself is fine and it's the game surrounding it that is problematic. Allied TD meta means it's easily zoned, but there is also the t3/t4 equation. The Ostwind is a monster now and comes much sooner, which... Delays t4, then you need to get ready for enemy tanks... Ect ect

Here's my suggestion for trying to streamline access to the brumbar:

Atm it's sort of set up to be t3 or t4 instead of the transition to t4 if needed

I would balance out the costs between bp3 and t4 building and increase the research time for bp3 substantially BUT give BP3 boons and improvements to the ostheer army that makes getting it more attractive and more of a transition.
Durability buffs/upgrades could be locked behind BP3. armoured skirts for armour that has them and the damage reduction for grens could be pulled from vet and unlocked (either passively or case by case as balance sees fit, preferably bought) and perhaps HEAT shells for the StuG this means even a player that PLANS to be using t3, it helps it scale. T4 is not a requirement to play Ost late game.

How does this help the brumbar? Well, the player is already half (or more?) way to t4 so if they happen to creep ahead and can spare the resources it's no longer a research that does nothing then a building then the unit. The cost of t4 is "cut" and more accessible if needed vs best if rushed.
The long research time on bp3 would be to sort of dissuade a rush in team games, since it takes up a slot in t3 queue, meaning no armour built/replaced while teching up.
I would also perhaps tie the werfer to BP3 but built in t3 to help making t3 a complete build (and make to voice announcer stop lying to me)

Maybe attatch repair dudes to the t4 building just to make it that bit more attractive and I think it could really round out the ostheer and make it easier to use the brumbar without it feeling like it needs to hit like a prenerf sturmtiger because of the costs needed to field it.

That's not downside, that's plain nerf. Again I'm not against heavily nerf any heavy tank but we saw in the past the outcome of it, more whine and buff again.
But just as a reminder, you value a unit from its Vet0 perspective, nobody is going to play with a unit that requires you to vet it to 3 or 5 to be good. (but I'm personally fine with that).

Downside is what make you opponent use his brain to counter you without having to call his own heavy. Popcap increase is a good downside since it makes you lack something on your army composition to afford the heavy and gives your opponent room to overcome you by other ways than brute force.

Heavies come earlier than they used to which has inflated their value/performance balance. Making it weaker to start makes it more manageable. It would be a nerf for sure, but a counter to the timing buff they received. My example numbers were rough, and absolutely flexible but a weaker and earlier hitting heavy ensures that I can still see use in small modes without commanding larger modes entirely.

Pop cap is a garbage solution because it puts 1/4 eggs in one basket meaning that basket HAS to be at least as good as 25% of an army if not better to be attractive. In the past high pop cap made heavies unattractive despite their great performance because it simply was too limiting to be useful. We have already tried massive pop costs and it proved ineffective. I'd sooner try something new that might not work than try the same thing that's been attempted time and time again and failed each time.

That giant flak HT always goes up around the 8 minute mark for OKW way before you get a Major. UKF is a joke, I don't know how anyone survives long enough to get Compay CP in the first place.

Maybe try denying the enemy the fuel or even capping your own? Idk what to tell ya.