Which operator should I retain: Ardelia or Chen?

For context, I have the following: Endmin with signature - I built him dearly as the on-fielder P1 Ardelia with Chivalric Virtues P0 PoG with the Thermite weapon P0 Lifeng P0 Chen Between Ardelia and Chen who can go? Although I do think later in the game Ardelia will leave the team once I build Last Rite but I doubt it'll be sooner — the leveling mats are hard to find and I am losing sanity fast (literally)! Also please tell me tips on how to do the combat rotations with these lineups because more often than not I just spam all of it. Endmin build in pics because why not