On the other hand the "two shot" kill from the mortar pit should be remove either by changing the timing of the mortar firing or by changing one mortar to barrage and the other auto-fire.
needs to be fixed. Thanks to horrible spacing, its entirely possible for a mortar to insta-wipe entire squads (OST 4-man squads) with literally zero reaction time for Axis, and with zero user input from the UKF player - it's insane.
It needs to be changed so that one fires, and half-way through the reload the other mortar fires. This ensures round spacing, gives Axis some time to react, and prevents 'zero-input' squad wipes.
The biggest problem is that OKW tech isn't very flexible. They usually need Mechanized, but back-teching to Battlegroup to get an ISG or two to counter the mortar pit is too expensive and time consuming. Ostheer can relatively comfortably avoid it and go for T4 and counter with a Brummbar or a Panzerwerfer (which can both shoot over obstacles and deal significant damage).
On top of that a major issue is that the Stuka is consistently ineffective against emplacements because its rockets have 0 penetration, which means that when directly hitting the 5 armor Mortar Pit they will "bounce" and cause only a measly 40 deflection damage (maybe 60 because of the target table but I'm not sure if the 1.5 multiplier applies to deflection damage) rather than the full 200 damage (it has the same issue against units like the Ambulance). This makes it noticeable worse against emplacements than the Panzerwerfer.
Because the Stuka is already very good as is and doesn't really need any buffs without reworking it, but that'd likely be too much of an undertaking at this point.
It seems like the 'easy' answer is to give the Stuka 5 pen (not 50, as someone else suggested). This would essentially only change its interaction with UKF emplacements, while leaving everything else the same. Its very unlikely that the "direct hit does less than a miss" nature is the intended
Alternatively, as you pointed out, OKW's tech is inflexible; maybe this should be addressed. The main issue, from what I can tell, is that going Med-truck leaves you too open to LVs, whereas going Mech leaves you without any strong sustained
indirect fire. As LVs are essentially a given in any high-level match, this forces OKW into going Mech first, every time.
One solution could be to give the Flak-HT an "AP Round" toggle (or timed ability) that gives it, for example, 60 pen - but zero splash damage. Due to the nature of the Flak-HT, it couldn't chase vehicles, but it could hold them off quite effectively. This could make Med viable against UKF in team-games, while keeping Mech unchanged. As a result, going med-first in these UKF/Sov match-ups would be viable, and emplacements less dominant.
Lastly, I wanted to point out that the Brummbar is not
a viable counter for emplacements behind shot-blockers. Its arc is fairly low, and will often hit either the structure or rubble when firing over it.