As a Chamberblocker myself i'll say that yes, with practice it can be pulled off with consistency both inside and outside of duels, in fact its more powerfull outside of duels since nobody expects it, and even if they do they think "****, this guy can chamberblock- panic!"
Side swing timing is perfect, it needs no tweaking, stabs are harder, but imo they should be harder- chambering them with overheads makes sence, you swing your sword up, colliding with their sword on the way.
chambering overheads on the other hand is stupid, not only is timing just plain weird, but you seem to stop it with the force or something. imo overheads should be chambered with another overhead.
my proposed chamberblocking:
-side swings block side swings as normal, no change.
- overhead blocks stab - no change.
-overhad blocks overhead, change of direction.
- stab blocks NOTHING. the animation simply doesnt make sense for blocking any direction, just leave it as an attack, no chamberblock needed.
EDIT: to the people who say the reward isnt enough, i'd say it is. not only does it give a great surprise attack, which is a free hit to anyone who doesnt expect it or doesnt have lightening reactions, but it allows you to controll the pace of combat, even if your opponent is highly skilled and blocks your chambers, you can vary blocks and chambers to suit your need, keep him on his toes and controll the flow of combat.