Maybe I don't know what I'm talking about, maybe I'm a person who needs to be told L2P and a whole bunch of other things, but here's a list of what I think needs to be fixed for the Ostheer faction. I will not comment on the other factions as I don't have the experience of playing them as often, though a few suggestion can be applied to the others.
I'll just generalize costs, no specifics for reductions.
Heavy Tank Call-Ins: Need to be tied to tech. Make Tigers/Elephants only available at BP 3, maybe linked to the Heavy Panzer Korp, but still called-in.
Command Tanks, Pumas, and maybe infantry StuG Es I think are alright, but could be moved to tiers or building requirements so as long as the other faction have the same treatment as well. Less call-in meta, the better.
Battle Phases 3: BP 3 and the tech building should be cheaper in fuel and maybe MP. At around 90 Fuel and 360MP(?), combined with the other Battle Phases and structures you're investing tons of manpower and fuel for even more expensive units.
MG42:This could apply to all MGs. Remann faster, able to retreat immediately even when the gunner is shot off before he reaches the weapon, just have the gun teleport at that point. Free instant reload when out of combat to it doesn't reload at the worst time possible.
Mortar: Can be applied to all mortars. Needs to immediately begin packing up upon command rather than occasionally waiting if the crew decides to reposition to tube due to someone coming from a different angle or waiting a few seconds after a shell is launched.
German Sniper: Health increased from 48 to either 64 or 80. Sure he's deadly but something even looking at him can mean a dead sniper and he already takes a lot of micro away from the main army to keep alive since you're going to be down half a Gren or MG along with having a very fragile unit in place of something that can hold the line better.
Panzer Grenadiers: Need more survivability in either received accuracy or armour so they can survive better against small-arms. They are used more for the AT support role than anything else from what I've seen. It may be the LMG problem, but they are outshined by Grenadiers in the AI department for most purposes, including cost.
251 Flame Halftrack: Needs to arrive sooner since it appears when AT or armour is hitting the field and those 120 munitions could probably go elsewhere by then.
and/or
Upgrade cost less so it doesn't break the bank for a unit mainly there for support that doesn't have range or suppression like the Quad.
Brummbar: Needs a lower price in fuel
and/or
Return its scatter value back to one.
It's an expensive vehicle meant to pulp infantry, support weapons, and structures while stunning/hurting the odd tank. With its long reload it needs to be able to hit its target and since rotating counts as moving, it can be hard to get the Brummbar to hit something if it decides to rotate even a tiny bit.
Probably needs hold-fire along with every other vehicle.
Panther: Give it the same accuracy as the OKW Panther, possibly reduce reload time from 5.8-6.7 to 5.5-6.0 so it can be more lethal against its intended targets, other tanks.
It costs 490 MP and 175 Fuel along with tech, it should be able to excel or at least do well against both mediums and heavies, but the long reload holds it back and most of the Allied tanks which are mediums, not heavy tanks. (Especially if the call-ins are changed)
Range is nice, but the Panther can't sight for itself(unless using scopes) and spotters can't always be available when chasing which is utilizing its speed advantage.
Osttruppen: You can't trust Osttruppen, no really you can't.
They're only good in combat when they pick-up weapons, but aside from that they're pretty horrible. They should at least do some damage. Yes, they fulfill other roles, but would it hurt for them to actually be able to beat other units that are in a bad position and them in a good one? Maybe increase base accuracy of their rifles.
Pak 40: Fix Target Weakpoint: needs work like the StuG where it tracks the target, not attack the ground where the target is/was at. This ability is almost pointless unless the enemy is standing still on flat ground.
Pak 43 and Howtizers: More resistance to being bombed/instant-gibbed by off-maps.
Pretty sure this is needed as it's kind of hard to protect these things if someone just peaks at them and then a button is pushed ensuring the loss 500-600 including vet since they can't move.
-Apply to other factions as well who have similar counterparts.
Maybe Needs Changing
221/222/251 HT: Both vehicles have continued to receive armour nerfs for reason I don't understand, aside from the FHT of the past.
Sure they're not dying horribly to infantry small-arms, but given their timing they could maybe use a slight durability increase. I doubt you'd be seeing hordes of 221s/222 even with these changes.
Panzer Werfer: Maybe a cooldown decrease from 100 to 80-90 seconds, though may not be needed if tech costs get reduced allowing it to hit the fielder sooner to build vet.
Delusional Change because we all need one:
StuG: I want my small target size back!
Those are all I can say for now, everything else is either fine, in my opinion, or I haven't used enough (Elephant). Any criticism or comments is welcome so as long as we can keep it clean.