The cobalt armor is always referenced as being part of the set associated for all-purpose use.
However, wolver armor outclasses it in every way.
I would suggest having the cobalt line be the only armor with resistances to all 4 damage types, but with the downside of not being particularly proficient at resisting any one of them. Then and only then will it live up to its advertized purpose.
The standard-issue weapons are fine, however, they do equal damage to all, and have powerful knockback potential to compensate for the average damage. It's just the cobalt armor that can't resist damage equally, and so is always at a weakness to elemental and shadow damage, which becomes important at T3.
>However, wolver armor outclasses it in every way.
And Gunslinger. And Demo, if there was an elemental variant of cobalt.
>so is always at a weakness to elemental and shadow damage
There is a shadow variant of Azure Guardian and its name is Almirain Crusader.
Both sets make fine costumes.
In terms of making an 'always second best' set, you could argue that is what Plate is for. Whether or not it achieves that goal is another question, much like the one you are asking - is 25%/25%/25%/25% normal/non-normal split better or worse than 100% normal? Or maybe it might get the Chaos-level love someday, who knows.