Spirit Caller Cave Makes Me Want To Die.

This is the worst thing I've encountered in my time playing this game. I've dealt with Margot, I've dealt with the Ulcerated Tree Spirit while having like 20 vigor, I've dealt with the god damn Tree Sentinel while not knowing how work the controller. Absolutely none of it was as bad as Spirit Caller Cave. The fat roller attack is genuinely undodgeable. I am at my limit and normally I would just give up on it. I don't even know what the reward is if I win. But I know I'm gonna have fight Fat and Skinny at the same time at some point later on. I don't think I can do that. I'm not sure if I'm physically able to do that. Even with the most brain-dead lion's claw + greatsword build you can think of, I can't beat this boss. How am supposed to beat both of them at once? Aren't they mandatory? Am just gonna have to quit like 80% of the way through the game? What am I even supposed to do?