Sometimes I really don't understand this game.
In one run I had good RNG for stats and was focused on speed - stamina training and got that bad B+

In the other run I decided to slap two power cards on it and got a very bad RNG for training (1 multi rainbow only through the two camps) yet I got a way better stat overall.

I just don't get it, are my stamina cards SO bad it's better to just put these power cards? I don't understand stamina training