I usually play as the Axis side. The Allied's AT guns always give me lots of trouble.
A tank cost 4 (stug) to 8 (panzer 4) or 12 (pather) population while AT guns cost much less.
A single AT guns can kill Stug easily even in a face to face battle (not to mention ambushed from rare). 2-3 can even kill a tiger very fast.
Could you give me some suggestion on how to counter AT guns? And against the computer, I can win in Hard mode, but not expert mode. In expert mode, the Allied uses AT guns with Thomsons and sometimes tanks. I just can't killed AT guns effectively. Thomson prevents normal soilders to get close to AT guns. So may be I should try to use more sniper and motors?