Should I change my Character Card Decks?

You only get one class type bonus, so two mage sets does not work.
Also, I find the class set bonus not to be SOO beneficial, compared to individual cards.
IF you have good cards, that ALSO make a set, then use it.
Without remaking new classes, and because you dont have many explorers to class change (expensively):

Deck A - S Mage ( I/L, Blaze Wiz*, Kanna) Level up your Blaze Wiz!!
Deck B - S Warrior ( DSlayer, DAvenger, Mihile/Hayato*) level up your Hayato
Deck C - S [no set] ( Luminous, Evan, filler)

If/when you SS your bishop, change your sets to something like this

Deck A - SS [none] ( I/L, Aran, Bishop) Aran is only for SS
Deck B - S Mage ( Blaze Wiz, Kanna, Luminous)
Deck C - S Warrior ( DSlayer, DAvenger, Mihile/Hayato*) level up your Hayato