Blood Letting Beast is virtually a large Beast Possessed Soul. Just look at them. Gascoigne's Beast Mode is a shorter, sturdier Blood Starved Beast in both appearance and move set, and pretty similar to Abhorrent Beast as well. Vicar Amelia is a white version of Cleric Beast, they both even have those little horns and have similar sizes and movements, and Darkbeast Paarl isn't too far off from either of them.
Bloodborne has three kinds of bosses. Werebeast/dog types. Humanoids. And Lovecraftian monsters.
Werebeasts/dogs: Blood-Starved Beast, Cleric Beast (which is really just a repackaged Manus), Darkbeast Paarl, Gascoigne's beast mode (which is a sped up version of Flamelurker), Vicar Amelia, Abhorrent Beast, Beast Possessed Soul, Watch Dog of the Old Lords, and Blood Letting Beast.
Humanoids: Micolash (Mauldron the Assassin 2.0), Martyr Logarius, Shadow of Yarnham (Vargh trio 2.0), Witch of Hemwick (Elana 2.0 with some Pinwheel and Fool's Idol mechanics added), Gehrman, Yarnham (Fool's Idol 2.0), Pthumerian Elder, and Pthumerian Descendant.
Lovecraftian monsters: One Reborn (Tower Knight mechanic plus The Rotten feature of having a guy on an abomination directing the monstrous body), Moon Presence (which doesn't fight or move all that different from Blood-Starved Beast, replace), Amygdala, Celestial Emissary (Royal Rat Vanguard 2.0), Ebrietas, Mergo's Wet Nurse (Darklurker 2.0 - especially with the cloning section and being hooded figures with multiple sets of arms and wings), and Rom (Freja 2.0).
Once, again, as I've already pointed out, the differences between a Flexile Sentry fight and a Smelter Demon fight, or a Velstadt fight and a Sir Alonne fight, are greater based on having an entirely different weapon and move set and exterior dynamics to the fight than a lot of these beast fights.
Of course there are similarities between bosses in ALL the games. In the end, are they still good fights? Shouldn't that be what matters? I wouldn't care if half the bosses in Bloodborne were werebeast fights if they were all done well, I just love pointing out this very apparent pattern because DS2 haters loved to point out "big guy in armor" complaints, even if these humanoid bosses in DS2 have a lot of significant differences and fight very differently. That being said, Looking Glass Knight, Ruin Sentinel, Pursuer, Burndt Ivory King, Smelter Demon, Fume Knight, Alonne, Velstadt, Lost Sinner, and Flexile Sentry fights all have their own interesting flavor and character, and all have their redeeming qualities.