Shamed by the opinion of some posters here, I made a new character aiming at a Dex / Faith build, fighting by parrying. I see that you simply have to learn the proper moment to parry attacks by trial and error for each attack and each enemy. Sometimes you have to parry right before you'd be hit; sometimes, as with spears, you have to parry earlier. I'm not sure I like that, I thought it'd be a skill you could acquire on early enemies and use it later on but with each new enemy I have to learn it anew.
that way the game would be trivially easy. imagine a new player learning this "universal parry" early (tutorial, firelink and/or early burg) and encountering that black knight or havel early on? suddenly 2 difficult fights become trivial. suddenly the news spreads that parry is the easy-win button for almost every encounter and the game loses a lot of it's charm and difficulty.
and it's not that much trial and error, pretty much every attack can be parried if you time it so that you press parry when the animation starts "accelerating" (i hope i made myself at least somewhat clear). that only requires you to know the attacks of the enemies, no real trial and error. just my 0,02€
- in thief armour, you can simply sneak up on balder knights and backstab them if you move really slowly.
you can do that in any light armour