Parry - Guardbreak - Free heavy (unless ur a raider, which has pathetic punishes). Repeat. Its basically what all the high level players do. Why even attack if attacking is way riskier than simply not attacking. This mechanic is probably what makes assassins generally OP in 1v1 duels, because their attacks are the fastest and hardest to parry. If your a slow class like raider, conqueror, shugoki? etc, its just too punishing to even attack in general due to the nature of being parry punished every.... single..... time....
If both players are extremely good at parrying and teching guard breaks, neither of them have any reason to attack, the match could be a stalemate, just because offense is too risky and will just lose the match, especially near cliffs where the first successful parry means u throw them off the cliff...

Being offensive and being the initiator to allow the duel to actually progress should be less punishing, I think the main problem is getting the free guardbreak after parrying, it just leads to insane punish. Allow the guardbreak to be countered, meaning if you parry, your rewarded with stamina drain on your opponent, knockdown if they had no/low stamina, a chance to start one of your own attacks/combos without the risk of being interupted by one of their attacks, and a bit of space incase u want to retreat, and a decent amount of revenge meter, and a bit of stamina recovery for urself, but NOT a free heavy or cliff push. This means that you can more safely attack without worrying about falling off a cliff or losing 1-2 bars of your HP for free, because you can tech or block after being parried, I think it would be balanced.