The Nito fight is probably the most knowledge based fight in the entire game. Meaning, when you just go into it, it seems ridiculously difficult, but with some knowledge, it's probably one of the easiest fights in the game.
I was getting raped by the combination of Nito's attacks and his freaking re-spawning minions. I tried some things, like killing the summoners/sorcerers outside his cave, thinking that might stop the skellies from re-spawning, but it didnt help. Also, rolling/dodging/ranged did not help at all, since after a while all his skeletons just wedge you in somewhere and you can't even move.
Finally looked it up online (I am not proud, but I had a long day yesterday, so short fuse). So basically a divine weapon puts them down for good, just like with the necros at the catacombs, and if you stay at the beginning part of the cave where you drop in, only the 3 small skellies aggro, the big ones in the back do not.
So once I put down the minions, it gave me a chance to experiment with the Gaylord himself. His attacks are super slooow and easy to dodge, but the miasma butt blast isn't. So I finally started using the Crest Shield to block it. It has like 80% magic blocking, worked like a charm. After that, 2 tries, and Nito was gone (ran out of estus on the first).
Funny thing happened in between. I had to go Human in between, to kindle the bonfire nearby. So as I was running to his cave in human form, some asshole decided to invade my world. I go oh crap, and realize im equipped with the Crest Shield and the Divine polearm, two things I never actually use for fighting, only equipped them for this specific boss fight. So I open up the inventory, and hurriedly replace them with my normal arms, hoping this dude won't attack me while im helpless like that.
Just managed to do it, he comes running in, BOOM perfect parry, take most of his health on the riposte, followed up by a finisher. Felt pretty good, in between Nito's bullshit.