Shrek is perfect at that cost. It has insane performance compared to allied AT. If it costed as much as a zook they would need to reduce the zook cost.
They're pretty similar. As someone who plays wehr a lot. I don't see the big deal. The USF mortar is easy to wipe and has near same performance and costs more than the Ost one.
As cool as the stuart is, it comes out so late for so much fuel and has an anti infantry 37mm but abilities that provide as AT. Though it comes out around the same time as a puma and is infinitely outclassed in almost every way.
Honestly I feel USF could use a rework much like OKW did.
For example teching to t2 is extremely expensive and only yields anti infantry redundancies. And with the new mortar the Pak seems like a sham. Why not replace Lieutenant and Captain with actual units to help replace the rifleman only strat. For example, the lieutenant becomes the mortar crew, the m20 is replaced with the wc51 and the tech cost is reduced for that tier. Replace the AA halftrack with the AT gun from t3. Replace the captain with cavalry rifleman so there is somewhat of an elite unit to really go into late game not locked behind a commander. As rifleman can easily be outclassed by 240mp grenadiers and require massive munition sinks to become anything of contest.
EDIT: Also the m10 is a cool little tank but coming out at CP8 is a bit absurd when pak44 and LEFH get to come out earlier or around the same time. In order to reach CP8 before you have captain you need to wipe nonstop or feed xp in hopes to get a quick m10. Not completely worth it IMO
These are merely just suggestions. I am curious what the community of CoH has to say.