Well, on one hand, I did one-shot Mergo's Wet Nurse, Gehrman, and the Moon Presence.
On the other hand, I was leveled up tremendously - not only having leveled enough to take down Orphan of Kos (who yes, I'm prepared to say is the hardest boss in the game) but also taking advantage of the absurd number of echoes available from clearing everything from the Micolash lamp to MWN to level up quite a bit (50 Strength and 50 Vitality,) which made me very well prepared to take on these bosses.
MWN was certainly the easiest of the three potential final bosses. There are a few nasty combos in there, and getting to the sweet spot behind it to avoid its slashes requires some precision, but ultimately I wasn't seeing anything mind-blowingly difficult to dodge.
Gehrman, on the other hand. I'm sure that before the DLC was out this guy counted as the hardest boss. He's super-fast and can parry you (though the one time he managed to do it to me he seemed to fail at his follow-up.) He gets a buff halfway through that seems to make him even faster. I did get a parry/visceral off on him. I think my biggest regret about Gehrman is that his Burial Blade - purchasable after defeating him and getting his badge (which you need to either die or Bold Hunter's Mark on Moon Presence to buy anything with it) - is skill-based, as opposed to Strength. I've got the stats required to wield it, but it's not going to be the right choice on this character. Guess I've got to get my Skill character up (she's only just beaten Cleric Beast.)
The Moon Presence was probably not as hard as Gehrman, but certainly has some nasty moves, including quick combo-swipes, a charge that tramples you, and tail/tentacle lashes that can get you when you're watching its claws. It also has a nasty ability that puts you down to 1 health, but it then pauses for a good long while after doing so, so you can regain most if not all the missing health by beating on it afterwards.
Before I finished up, I made sure I got every important item I could get, which sadly involved killing some friendly NPCs like Djura for the Ashen Hunter set (which you actually get at the Insight shop after killing him,) Adella to get the Oedon Writhe rune (there's a better one you can get off of fake Iosefka if you confront her before beating Rom, but I waited to get her Third of the Umbilical Cord, which it turned out I didn't need, as I'd gotten Arianna's and the ones at the Hunter's Workshop and off of Mergo's Wet Nurse.) I also got the Eye rune off of Willem. I know that some of the other characters (mainly the Chapel Dweller) drop runes, but they seem to be lower-level versions of ones I already have. I felt bad enough killing the psycho nun and the brain-dead professor (not to mention the noble Djura) so there was no way I was going to take out the Chapel Dweller, possibly the most benevolent character in the game (you know, barring some weird interpretation of his character.)
As far as I can tell, the only important items I'm missing are the ones gotten out of the Chalice Dungeons (which... is it worth it?) and the whistle you get from doing the League quest chain, which I believe requires co-op play.
Anyway, beating the Moon Presence leaves you a whopping 230,000 or something blood echoes. You need to visit the Hunter's Dream twice (unless you intend to, you're probably not going to die on the way to the Central Yharnam lamp this time, and you will of course have plenty of Insight to see the doll - she's just inactive the first time you get there even with Insight.)
I have to say, I've had a super fun time playing this game. New Game+ awaits me now, and I'm sure I'll play a bit of it, but I think that it'll be a good time to take a break from Bloodborne, probably go back to the Witcher III. And I'll want to do characters based on other main stats as well. I've got my Skill character, but I think next I'll do an Arcane one. Eventually I figure I'll try a Bloodtinge character (wonder how that will be before I can get the Chikage...)
And at some point I'll either have to go back and try to finish Dark Souls or maybe just skip ahead and play Dark Souls III (I've been advised to avoid DSII.)