I voted for Buffing armor, nothing dramatic, just +10% armor on all body armors. With all the strenght builds and ranged spam these days, I think it will improve the gameplay and would also make ironflesh a bit more useful than just a place to dump extra skillpoints into.
Also voted for nerfing polearms, the only needed nerf is removing polearm stun. The old argument was 2H have lolstab, polearms have stun - since 2H don't have lolstab anymore, there is no reason for polearms to keep their stun. Removing it would make 2H and polearms equivalent : 2H have better speed and animations; polearms are longer, a bit more damage (+bonus vs shields for high tier polearms) and offer more versatility.
As for cav, the only necessary change would be adding a trample sound that can be heard from distance. Now you only hear it at point blank when unless the cav misses you are already dead, and having a horse silently gallop towards you is a bit silly.
Generally cRPG is more balanced then ever, apart from the things I mentioned above, only some internal class balancing is needed (for example Huscarl is still by far the best shield, Arabian Warhorse the best horse, etc).