That was my "favorite" non-story/big optional boss on my first playthrough. It's actually pretty easy if you happen to be using a huge club or hammer. Otherwise, have fun with your mace if you have low STR. You can also cheese them with a particular magic, but it doesn't make the fight any less annoying.
Yes. They are the boss of the Sellia Hideaway.
There also seems to be some kind of negative edge going on too, or maybe it's just my controller. I cannot count how many times I've dashed forward with Bloodhound's Step, hit my attack once so that I'd thrust after the step ended, only to thrust and then swing again. I'm like "WTF? I swear I did not mash the button!".
It doesn't really though. Although it might depend on what build you're using. Trying to do that with Sorcery (as that whole area is tied to Sorcery stuff) gets you a whole lot of "Haha, you want to cast? Nope, nope, nope, nope" as the spear wielder will not stop dogging you with its stupid hop-thrust that seems to go on forever. If your summon is on that, have fun getting hit by the rings of the other, and the constant Crystal Torrent spray of the third.