Only boss in any off the games ive had a problem with is the giant rat in ds2.
That thing has the worst hitboxes of any enemie ever. It hit me in the back when I was in front of it with a shield several times. That with the broken camera just made him a pain.
That thing was total bullshit. It doesn't even look like a rat - it's a giant scabby dog.
"Don't use lock-on and attack it's ankles" is not a clever solution to a boss fight, it's an admission that your targeting system sucks balls. And it's particularly unforgivable in a game where you could lock on to a previous boss's ankles.