Hi, I'm new to Panzer Battles

[Ekaton]

As in the title - I'm new to the Panzer Battles series, playing mostly WWI battles and squad battles from JTS so far, and I have some questions.

I've just finished the Utah battle from getting started and it was really tough. I managed to take most of the coastal bunkers but with quite heavy losses. 

First of all - my artillery was useless. Even when concentrating my whole artillery in one place, most of the time they didn't kill anyone at all. The best I've got was one dead. Same with the aerial support. Is this how it's supposed to be?
Second, It took several repeated assaults to clear a bunker - I combined my infantry, engineers, tanks... nothing worked. Each time I had about 1 dead on each side, sometimes 2 Germans dead, sometimes none. Is there any trick when assaulting a bunker? I mean, 200 men vs oftentimes less than 10, and still - nothing?
Third, what's the best way to use your tanks against infantry in bunkers? Are they any good when assaulting? They were not very effective when firing against bunkers anyway.