Discussion on the unofficial Spiral Knights discord server had us come up with some interesting new ideas for how to approach defense - invinciframe length!
I'll make this simple - glass cannon sets would have no invincibility/mercy frames upon being hit. Class armors would have the current invincibility frames upon being hit. Defensive sets would have slightly increased invincibility frames upon being hit. Plate sets would have a fair bit more invincibility frames upon being hit.
Basically, the more defensive a set is supposed to be, the longer they are invincible after being hit, and the inverse for offensive sets.
This means mixing gear types for invincibility frames would be a valid choice.
Those frames could be accompanied by the SFX of a shield being hit each time we take a hit during those frames and some kind of aura or glitter that indicates the streght ofthe effect.
Something like: Blue is the strongest and fades into red as it wears off. Weaker armors would start at yellow and fade into red much quicker.
(I hope I made it somewhat clear :/ )