I just finished Baranovichi campaign on hard as the Germans and won almost every battle and on the campaign I actually encircled and destroyed all the southern Russian forces and retook Ssluzk. the computer simply sent most forces north to defend the bridge at Stolpce and did nothing. I played on hard as the russian and took Baranovichi in 3 days.
I think the computer needs more victory locations to attack, similar to SOW (scourge of war) then it might be more aggressive. starting Orscha on Hard as the Germans tonight, see how it goes