I would also say, do not forget to add one or two tank destroyers to your group. True, they start out a little weak, but if they gain some experience and get upgraded to StuGs, they are your best bet against T-34s. These guys are also very adapt at takin gout bunkers.
Apart from that, I will say that the most important thing is to know how to best utilize your units, and what their weaknesses are.
Tanks crush infantry in the open, but infantry kills tanks in city/wooded/hilly hexes. Artillery are very effective against soft units, but are very vulnerable to attacks etc etc.
Another thing to keep in mind, is that although the game is called Panzer Corps, and that when people think about the German Army during WWII, they think of tanks, you cannot succeed with tanks only. A mixed pool of units is a must!.
"Hun skal torpederes!" - Birger Eriksen
("She is to be torpedoed!")