Whenever you feel like moving on!
Some tips
- You can break their guard with a kick
- They'll try to punish you for backstab attempts with a shield bash. If your weapon is fast enough, you can hit them during the shield bash animation before they can pull it off
- The ones with the sword are easier to parry imo. They like to do 3-4 hit combos. Easier to do a "setup" parry than try to parry the first hit. Block the first one, and then press L2 when the second swing is about to hit you.
- You can also get them in a parried-like state. If you break their guard and they appear stunned, walk up and press R1 (don't press any direction) and you'll do a riposte-stye attack.
You can get through the whole game without using parry/riposte if it's not your thing, but these guys are good practice