For the infantry, I use them as bait for the slow turret-moving Tigers so my Shermans can hit the rear :-) :-) :-) I also use them to detread the dreaded Jagdtiger.
Paratroopers on the other hand can be deadly. When there's fighting in front of you, drop them on the rear of the enemy. He wouldn't have time to choose who to shoot.
The most useful infantry aside from the sniper is the officer. Though he may also be a meatgrinder, he's added range from his scope is better than nothing at all.
I believe you can't win the game solely with tanks alone. You would need some kind of support (SPGs would do). Else, keep waiting for aircraft to reload and use them extensively, problem is, don't let them get shot down.
If you want a good strategy game, I recommend these:
Company of Heroes - slightly on the enjoyable side, but not on historical accuracy. Inf here are dangerous as tanks.
Soldiers: Heroes of WWII - most accurate I've played so far. Tank damages vary, and you can even equip your infantry with the Sherman MG :-) :-)
Faces of War - an updated version of Soldiers, though not as good.