The stuka bombing is unavoidable, there's no smoke alert for soviet side, a mini V1 with 60 seconds cool down LOL
Don't clump any unit up, it takes quite a while to come in, and it does not kill unless direct hit. So if you loose 3 squads because you were not paying attention that is the whole point of the game. Unit awareness. If you hear that sound, and you have ANY units clumped up SPREAD THEM OUT. It is FAR from unavoidable or OP. Know what you're enemy has line of sight on, generally the only place they can drop it is on a main engagement. Do a better job of staggering out you're forces and no problem.