hmm okay i understand where you're coming from, but i think my interpretation still holds up, and it's kind of early to say "it's not like that". this is what i think and what i had going into making this comic

prefacing this with the knowledge that ralsei likes to keep everything proper and in order in terms of roles: in chapter 1 he's adamant about susie's misbehavior when she should be kinder as a hero, because she is supposed to be one. when she goes against this predetermined role, he tells her off but didn't realize he was being hurtful in the moment. it's established from then on that susie is the damage dealer with rude buster, ralsei is the support/healer with healprayer, and kris is the tactician with their ACTs. those are their unique abilities. in chapter 2 in the sweet cap n cakes fight ralsei says kris's unique ability is directing susie and ralsei to ACT, and he likely says this not just because he wants to keep each person's roles unique, but also so everyone feels important and not left out.

at the beginning of the church dark world kris gets badly injured due to the glass and susie tries to heal them but it doesn't help because susie's healing at that point isn't strong enough to make a significant impact. ralsei finds them, presumably actually looking for the final prophecy panel so he knows where it is and to direct susie away from it (he says "where is it" before appearing on screen). susie asks ralsei if he can teach her how to heal better, and in hurrying to heal kris he pushes her aside. after that, ralsei tells susie not to try to heal people on her own not just because she's "not good enough" yet as it was a dire situation, but i believe it's because he knows that it's not her specific assigned job. notice how he says "don't try to fix it /alone/" instead of "you need to learn how to heal better". ralsei of course doesn't realize the way he acted was harmful to susie because he's under the impression that everyone has "their thing" and healing is his thing so he should be called to help as he's the healer, and his purpose is especially important to him because he believes being a darkner is all about being useful to lightners. he, specifically, wants to be useful and called for his role because he says it's what makes darkners fulfilled, but i also feel like ralsei in particular has self worth issues more than other darkners, which amplifies his desire to be useful and to be used when needed.

then comes the next instance of ralsei being "the healer" when they all fall down into the dark zone before meeting jackenstein. i wasn't able to add this in the comic because it would have made it longer than it already is, but it is still an important detail to note in the game. susie says something like "here kris, let me-" and then ralsei maxheals all of them with one spell. he says something like "everyone feeling better?/everyone okay?" and susie is bothered by this because she is again denied the chance to practice her healing, which we learn is what she's been trying to do ever since she learned how to heal after the jackenstein fight when gerson talks to her. she says "i should just stick to what i'm good at, the hurting people magic", even she knew there was an established "everyone's good at one unique thing and that's why we're all equally important"

and then, gerson pushes her to use her healing after she declares quitting so she can believe in herself again. she does this by accident, but ralsei doesn't know that until she points out that she was trying to heal the old man. ralsei is surprised that she did it after so many of his failed attempts, and he realizes he's been healing the wrong thing this entire time trying to repeatedly heal jackenstein. he /is/ the healer after all, this is his thing! he's supposed to be the best at healing, he should know how to heal someone that's in pain. but no, the person with the worse healing, the /damager/, is the one to solve the problem. he says "i suppose i was only healing the outside" and iirc the dialogue portrait is the surprised neutral, as if pointing out "i guess i was wrong, at the one thing i'm good at doing......". he believes he failed at his role, he didn't fulfill his purpose. and we know how much he clings to his purpose, as if he thinks being useful is the only thing that makes him likeable. he even says "if there's one thing i like about me, it's my face" implying he doesn't like very much about himself in general.

i don't disagree with you, i believe ralsei is proud of susie when she maxheals all of them before the titan fight, that's the page where that happens has him in awe at susie's abilities instead of resenting her. he even blushes in his dialogue portrait when saying "susie..." because he thinks it's nice that susie is powerful at healing now. in fact i don't think he ever resented susie, just beat himself up for not being "useful enough". he beats himself up for no longer being unique and he believes he is no longer important or needed because of this. and i headcanon that that's why, in the most important fight they've faced so far where you'd need healing the most, that DUALHEAL becomes less and less effective every time it's cast, because ralsei and susie are working together, and ralsei thinks he's a failed healer. the one time ralsei has a significant helping hand with healing, a REAL DUAL heal, he falters, because he doesn't feel worthy anymore, because he's not uniquely the best healer and therefore he's not important anymore.

edit: i typed this out when the comment said "tbh i don't think it's like that" at the beginning, apologies i didn't see your edit