It took a while, but I beat bosses 3, for and 5.
Boss 3 was tricky because his animations had to be countered with very accurate timing, so it was a bit of a struggle.
Boss 4 kept hitting me with an unblockable attack, and the tip about attacking instead of parrying didn't register until later, so I ending up blocking his dash attack, dashing, attacking twice, and then dashing away before he struck back. There was also a slight delay after his unblockable attack that allowed me to get some damage in.
Boss 5 honestly felt easier than Boss 4. All of his attack patterns had clean animations with clear windows for parrying and attacking (double sword slice, triple axe swing, overhead spin attack, quick dash), even the ranged attack (it was a deterrent for approaching at first, but even that can be parried for an opening). More importantly, his triple axe swing always used a special third hit, and it was very fun to attack during that last hit to gain another opening.
Overall, this was a very challenging and very fun game. I can certainly see the similarities to Hollow Knight.
I'd be interested in any projects you have in store after this one.