well to be honest i wasn't aware you were planing on adding party members, i just said with what i had as impression as i played so i did not had in mind of the whole recruiting allies idea, so it fine if there are things you wanna keep that way
also as i read your message i decided to check the part where marcy fights the knights again so i could test out her playstyle again, it possible that the cerberean strikes may be a bit too strong,like it could deal 5 damage on each hit so i may could suggest to debuff it atleast to 1-2+atk,i did a second play run on the knights fight but this time only by attacking and not using the skill, marcy can take on a total of 3 out of 7 knights with no criticals involved before being defeated, which i think it fair for someone that is a warrior build but it your call mostly