I also encountered the hit from above issue with whale but just thought it was a positioning issue so I'll definitely extend the hurtbox
You can hit cannonballs in the water to make them sink faster which I hope players will attempt, it's an issue that has to be tested by multiple people to see if they think about it.
The poison clouds are supposed to be evaded be positioning, they do hover pretty high above the ground
Slime is just the tutorial boss, I nerfed it heavily after some people got filtered by it(the hitboxes were too big though)
I have some whacky moments on regular "levels" between bosses and another addition planned that could happen during bosses
Lack of "hook" is a massive issue for a commercial game so I'll have to do better for my future games..
It's tough to tune bosses well without other's feedback because you I get too good in my own game, I already know I can't jump clouds or I can hit sinking cannon balls..
I appreciate the in depth feedback and I'll definitely tune several things based on it, thank you!