Could the Windrunner Shoes end its flight buff only after you've landed when changing direction? Was flying across a hole and stepped sideways onto land but still got a gravity death.
Lastly, the minions summoned during the boss' final hp threshold is constant which means your party becomes redundant because they are always fighting minions instead of the boss. Even then, they can't even distract or kill them quickly enough to let you focus on the boss.
To sum, the difficulty ramps up terribly at the end because the boss spams a disproportionate amount of runes and minions at you until you die.
About the final boss' difficulty:
The boss' final hp threshold causes his floor runes to be spammed far too often. It causes more damage than his point blank cloud attack to the entire party. Dodging the runes becomes near impossible as the minions fill the arena, blocking your view or hitting you. The runes themselves explode almost as soon as they appear, giving you little to no time to evade considering the area they cover.
Moreover, hero's movement stutters when more enemies appear (to point of slowing the game) and increases the amount of input required to keep him out of danger yet within striking range. This might have to do with the game's optimisation.
there's a problem with the Ally's AI where, if you click to attack an enemy that's outside of the border (spit flower on isolated floating island), melee type allies will be stuck trying to attack the out-of-range enemy and will not change target until you re-enter the area
 "Cardinal Quest 2"){kind=icon}
 "Mighty Knight"){kind=icon}
 "Cloudstone"){kind=icon}