Every enemy in Zelda 2 has a weakness. The armored knights you speak of are actually incredibly easy. What you have to do is jump and slash them while you are in the air. You will land a hit and knock them back every time no matter where they have their sheild.
Just a pro tip!
Let me start by saying that I like ALL of the Zelda games. There is not one I truly dislike.
Now my fav is a toss up between Twilight Princess and Skyward Sword, but if I had to pick one I would say Twilight Princess HD.
My least favorite was Triforce Heros. I liked the game, but I got...