The puzzle to me was in stacking defense instead of offense. Typical souls strategy is get high damage and kill the boss before it kills you -- with ancient dragon that was entirely reversed. The physical meleeing portion is dull and repetitive (stand in toes, hack away.) It's not a puzzle in the Zelda sense, but as in "there is a right way to approach this."
Sinner was a good aggressive boss with the emphasis on WAS, she got nerfed and so lost that charm -- but in ng+ the pyros change the dynamic enough that you have to switch up how you play, at least initially until you kill them.
I don't get people's complaints about small areas with bosses (capra I can understand) -- you have more than enough to dodge and lead Velstadt, none of his attacks cover the whole area. But then, some encounters are meant to be closet trolls as that is the point of the arena -- to limit your movement and force you to come up with a new way to face off on the boss. If every boss was a big arena, it'd get old very quickly. Even the dull big knight bosses like dragon rider at least had some gimmick, with death drops or an archer platform or something. Regardless, as said, shit's subjective cuz it boils down to what you _enjoy_.
There's people who think wandering congregation in ds 2 was shit (it is shit) but think deacons of the deep in ds 3 is cool. I can't even bother to understand what drives their thinking
Clockwork Knight oh right, yes, looking glass was definitely a cool fight too -- especially after they lowered the volume on the thunderclap effect. It's a damn shame how quickly you can kill him in ng+ tho, they should have him summon squires at an earlier time.
edit: Rotten is a very easy fight to me, but I still enjoy it overall. There's different things going on, and his derpy appearance, weird music, and overall tragic state + makeup is good presentation. The fight itself isn't anything groundbreaking, but it is fun and if its one of your earlier experiences then the fire hazard can actually affect you.