Generally u want to maximize either the hp stat or tai/nin, depending on ninja role. Also decreasing the lowest useful stat: def on ninjas, that are backline or tai/nin, if any ninja doesnt use it.

Roshi +hp, -atk

asuma +nin -def

iruka +atk(dmg) +res (shield) -def

darui +nin -def

bee dont have him, but propably same as iruka, since he fulfills same role

roshi is a bit special, since u for 100% want to max his survivability and scaling def/nin can make up for it if you want to decrease tai dmg stat

\/ thx, that's what I was missing with roshi. I dont have him so couldnt check growth rates.