The guard break countering timing should be the same when your opponent is in full stamina as it is when they are in low stamina. I can get the gbc 85% of the time when they are in full stamina, but as soon as they gb me when their stamina is low, the timing window is so much slower and extended to counter it properly, and I always miss. This gives them an advantage in low stamina to gb. The timing should be consistent whether full or low stamina. It can still be slower for them to fully gb you when they're in low stamina, but the timing window where you can counter it needs to allowed just as early, and extended for a longer duration.
Also, it's bothering me that some characters have an unblockable cancel option. This should be uniform across all players. If one character has this option, all should too.