Need help, These are my heroes, Any suggestion/advice?

Hello fellow Merchants! Thanks for your time.

These are my actual heroes (Excluding a 2nd Warrior i just bought)

Any advice on how i can fine tune them, some thing you would change, equip or aim to, please tell me

Also, each time i have a fight with Kirin, he wipes them all. any advice on how to beat the crap out of that guy?

Thanks!

Edit: Thanks for all the detailed advices! Yeah, as u can notice i was "progressing" with some weeeird stuff, so now thanks to you i have some work to do, i'll update when i change a few things. If u can share moar of your merchant wisdom, please, do so!