imo incendiary rounds are not certainly bad. I personally am quite fond of them, as they actually force mgs and such to reposition more and leave them more open. It could be stronger, but then it would require either cost increase or increased scatter to be fair.
As for ostwind and hetzer, the likely issue with that could be the timing of the 2. If i understood correctly that if you built ANY, og the trucks (like battlegroup and mechanized) it could lead into particurally annoying rush that opponent might not have enough counters for. I think battlegroup hq was 30 fuel and mechanized hq was 45 fuel (plus 15 per truck) which leads to 105 fuel for both hqs and 100 more fuel for ost or hetzer. compared to battlegrop to panzer hq and pnz 4 = 320 fuel (i am not sure, you can correct me on any of these numbers). I think it could lead to issues being able to rush out effective anti infatry tanks that early, but i am not very informed of okw timings, so correct me if required.
In fact,I'm not sure what’s the timing should hetzer show in the battlefield.....but ostwind really need more early timing,or use “brummbar” replace ostwind and produce in T4 more better