In every battle that I've played thus far, there's always a situation that you can't control which pops-up at the most inconvenient moment. If you're lucky, it will just result in track damage or possibly a killed crewmember. If you're unlucky, you'll lose a tank, maybe more.
There's a notable increase in performance when you get medals/awards/abilities that improve the capabilities of your tanks, so later battles are not necessarily more difficult as long as you get a feeling for how to use your forces.
As your tanks have better guns, you don't need to sneak up on T-34's to shoot them from less than 200 meters, something I generally have to do, so provided the ammo situation remains good and you keep your Panzer IV's alive, you have a good chance. With Panzer Ace, their HEAT ammo might even be able to destroyed a T-34 from the front.
Your experiences thus far mirror mine for the early battles. They're not too difficult, but there's always some tricky situation. Of course, I restart when I lose a tank or crewmember and you keep playing, so I'm hoping your core will stay fairly intact.
WitE Alpha tester
Panzer Corps Beta tester
Unity of Command scenario designer