The final boss is probably one of the hardest ones, the last phase in particular. I ended up upgrading Snake armor since you're in water, and Ring of Fire luckily works in this case (and it should, because the final fight shouldn't lock out a build). This armor gives you health regen in water, with RoF its even more ridiculous. Not to mention the stamina buff you get from the full set.
Then I did NG+, talked to my girlfriend on the phone with the game on mute and when we stopped calling I just entered Chapter 3. Then you see how much you've progressed as a player, ofcourse everything is unlocked now but I evade a ton, abuse counterflow etc.. I run rock solid and no cloud step. I one shot both chapter bosses while talking. Chapter 2 shot up in my ranking, its actually not that big and it connects well. I let things play out different now, such as the 2 stone warriors duking it out and the order in which I killed the rat bosses.
I don't think I've played another game where respeccing is so fun. I also like it in Dark Souls mind you but it comes at a cost and its limited. I tried many, many builds during my first run. I went Centipede armor poison build, RoF build, Pluck of Many centered build, Golden armor Qi regen build etc. Changing your Curios, drinks, soaks and spirit can all play into a certain build, like self poison soak with a gourd that gives another attack bonus upon use. Or a soak that extends Ring of Fire duration and relic that gives a level 4 charge inside it. Its also worthwhile to spec on Bane protection for certain bosses, it greatly diminishes the effects. I never bothered with it until chapter 6.
The game has its flaws, indeed the invisible walls, and some boss balance and hit boxes are questionable (some big bosses like Duskveil actually evade a ton of attacks despite being huge, I hated these fights).