1) Nobody can't shoot through hills or trees. I might just look like that, because the actual flight path of the enemy's shell is not rendered in that detail on your computer then on his. Actually he is shooting just over that hill. Of course that works in both ways - if you shoot at your enemy, it might look for him the same weird way.
(Sometimes when you see an enemy taking down a town, you will notice buildings exploding while the shell still continues it's path, landing way behind the town. This is for the same reason)
2) "I'm getting shot by tanks I can't even see, unless I zoom out.
They are just little black dots then. If I zoom in there are trees, a hill or something else between us."
You basically gave the answer yourself. Depending on systems settings, distant intervening obstacles may disappear, while the tanks behind them are still visible. The exat distance at which that happens depends on detail setting. But don't worry, this is a bug that HTC has already identified and it will be fixed in next update. We are expecting it very soon.
Also, hit Shift-F4 for a ground view mode that might help you spot GV's at greater distance. Shift-F4 gets you back to standard.
3) 2200 is a darn long range in WW2 armored combat. With proper shot placement, a Tiger is able to kill a Sherman Firefly at that range, but it's not unreasonable that shots might also glance off.
Distance, angle, sloped armor, armor thickness, exact shot placement are all important in getting kills.
