but you just said you want them weak for balance...
but hey, i like the piercing-willbreaker idea. brynn doesnt need a makeover, she just needs to do a lot more damage to make a difference.
but since you are talking about ezekiel/herja, i would love to see ezekiel do something that differenceates him from herja other than more defense. so i think it would be great if he would become the ultimate debuffer/buffer so for example restores/drains morale but instead could do for example random healing or random stunning. like there is a 20% chance to stun target while drain morale or a 20% chance to restore HP and morale... something like that.
EDIT:
tbh though, i dont think that calvin needs a makeover coz if you get lucky in formations setup then the rendering a hero useless for an entire match is a huge advantage since he can skill every round with the right spirit (remember if he skills first then the normal hit from the one he just drained puts him right back on 100+ morale).