Out of lurk mode again already… oops… 
No, daggers are very affective against metal armor. Any point-on weapon attack is. Plate armor negates edge-on slash attacks where the surface area is large. Hit a tin can by swinging a sharp knife 
edge-on, at it. The can 
likely bends and dents. Now stab it point-on… it slips right through - almost effortlessly. And a tin can is about the same as plate armor of old. Chainmail was invented to try and negate some of the puncture that plate armor was so susceptible to.
Maybe these considerations are too complex for CE tho? At least in it’s current state?
Sure, that’s a totally different thing than knowing how a single weapon 
behaves and what is good or bad about it.
Because we’re not talking about using all of the facilities in the combat system to make an affective and successful attack or defense. We’re talking about the aspects of a single weapon and it’s behavior. Players will always find the most advantageous combinations of potions, armor, weapon rotations, weapon mods, food, movements, and so on, for the play-mode they’re in. That’s a different topic IMO.