Notes from author
My first build. Tweaked to be more optimal. You REALLY don't need 50 dex, you get five extra points of damage for ten levels. Lowered strength a bit and sacrificed a few more point to get to 40 endurance (stamina caps there) and upped vitality a bunch. For the tiny bit of extra damage I traded in, the assassin now has a lot more health. This should make trading less suicidal (not that you would do that, would you, R1 spammer?) should you need to.
This build is all about style, trickery, and getting into your opponent's head. Switch out your shield to the parrying dagger if you're good enough/feeling brave. If you're REALLY feeling brave and stylish, switch out shield and falchion for daggers. Dual daggers combined with shadow gear and flips will make you look badass.
It's all up to you. Use that sword and shield if you want. Using a parry dagger is pretty good practice though.