Which cards should I use?

why do people keep getting the mage set it's awful

The same reason I make a warrior deck. The individual effects are appealing but don't fit into a job set (applies for hayato, zero, and kaiser) so wynaut?

Kanna and Beast Tamer can't go in a set, and most of the Heroes card effects are horrible except Lumi for Mages (Merc utility is small, Evan only for dojo) so those three fit in a set well.

BTW in your setup you can swap kanna and hayato for free lolboost and replace merc with a mage if you want if CD reduce isn't useful for an even less lolboost.

Unless there are other individual cards that are worth more, ofc.

On the same note Pally Bucc and TB cards are horrible never use them.