A: Cavalry do not ignore terrain battle dice reductions. This DOES make them weak. (It's WWII, after all.)
The only good use for cavalry would be to pop up as reinforcements on the opponent's baseline (like Armor Breakthrough) to attack 1- and 2- figure infantry units that have been pulled back. Someone should make a scenario like this!
A: There's a new (June 2013) official scenario involving Italian cavalry: Battle of Agordat, Eritrea/Ethiopia in 1941.