I prefer an increased attack stun. At least enough to prevent the attacker to try any kind of lame double hit trick.
Also, if the balance team believes long and heavy weapons should be globally nerfed (or, equivalently, that short and light weapons should be buffed), what about increasing the recovery time the longer and the heavier the "deflected" weapon is ? It only makes sense a big ass two handed axe is harder to put back in ready position when your swing has been deflected, than a much lighter longsword for example. Also, this could apply to any swing that only hits air.
As for balancing it with chamberblocking, maybe chamberblock attacks could be faster so that it actually rewards the ones that pull off the move. I recently chamberblocked someone on purpose in siege mode just for the heck of it, and the guy just blocked my attack. Chamberblocking is very high risk, almost no reward right now.