I've been bothered by this for a while now. Jelly armor. Why is it in this game? It serves no purpose. If, for some reason, I want armor that grants piercing protection, I can just get Cobalt armor and a Defender-line shield, or any of the class armors (excluding Guardian). So, here's my proposal: Make special damage protection the special of some armors. This is gonna be long, so bear with me.
Here's the jist of it: So, until you get to the 5* variants of most armors, almost all of them protect against piercing. So, change it up a bit. The class armors have different specials (like bonus sword damage), right? Well, if they have that ability, then why should they also have a special damage resistance? Get rid of them. HOLD UP. PUT DOWN THE PITCHFORKS. Think about it. Since these armors have piercing resistance (and more at 5* level), they render Jelly and Cobalt armor useless (And eventually all of them with the exception of some shields). If you have all three 5* variants of Striker armor for example, you not only have all your bases covered in protection, but you also keep the benefit of having increased swordsmanship ability. You have no need for Arcane or Skelly armors. So, rather than have them protect against all damage types, have the thing that makes Skelly and Arcane and Jelly armors useful be that they're the only armors that protect against their particular damage type. Then, do something else for the 5* variants of the other armors. Like this: Vog cub: Swing Speed. Sklover (never spell this one right...): Movement speed. Snarby: Sword Damage. This keeps the special damage armors relevant to the end (and makes Jelly armor actually useful!!) Just a thouught.
It's more of a costume set, rather than a utilizable suit of armor.