Orphan of Kos is the only *hard* boss

I've played every souls game and now I've finished Bloodborne. What strikes me as unusual is that Kos' orphan was the only boss that I found to be difficult, like actually difficult. There were challenging bosses that took trial and error such as Lady Maria but that's as hard as it gets, the rest of the bosses are easily defeatable on first try without summons or take a couple of attempts. Orphan of Kos is extremely aggressive on par with Ludwig except that it's hard to stagger him and he relents no matter what, only a select number of attacks are realistic to parry. Its the only boss that took me plenty of time to learn the moveset.

Anyone feels the same way? I'd also say DLC bosses are far harder than main story bosses.