Only thing worth dismounting is Druzhina cavalry. I use steppe as russians and rely on Druzhina to be my killer infantry alongside Rus Spearmen (Set them at one side of a bridge and you're talking 400 kills. They're bloody good in late).

Oh, and dismount feudal sergeants if you're facing a cavalry happy opponent I think, but im not sure, that they give standard Feudal sargeants (if less than a standard unit).