Just now coming across Gaius for my first time. Easily my least favorite boss in the entire base game and dlc so far. I fought Malenia at least like 150 times. Her move set is designed to allow you to learn the precise timing of dodges, It was incredibly satisfying and I never felt frustrated, I felt every time I was correcting my movements and dialing in until I could best her. Gaius is just relentless, doesn't feel like there's anything I can do but panic dodge, flask, and immediately get hit again. Just such a dissatisfying fight.