Currently it costs less stamina to Guard Break an opponent then it does to counter the Guard Break. In short, you get into a scenario where you can guard break your opponent until their stamina is drained entirely, provided they counter the guard break. What's the alternative, get thrown and let them get free hits?

Guard Break Parries need to be either stamina-neutral or favor the defender, because in their current form the person who starts the guard break chain will simply exhaust their opponent.

This happened on every character we tested it with - the person who started the guard breaks would end up with full stamina while the defender would be drained in 2-4 parries.