1. Do not try to go for Deflects. If you deflect, do not do the followup stab. Hyperarmor will give them a heavy and they will always trade better than you.
2. Instead, go for a parry. If the enemy feints alot just throw in some zone attacks or lights occasionally.
3. PK has a hard time to open up turtles. Try heavy - soft-feint into guardbreak.