Yeah, I feel like the health/damage/heal dynamics are poorly balanced in general. It's particularly evident in the boss fights, where their huge health pool and damage output often makes them impossible to counter for an average build. Or, more precisely, my hunch is that the game doesn't allow enough room for player skill to counter bad luck.
And the same issue is spread across sequences of fights as well: the loss of health becomes a compounding problem that travels with you from fight to fight and results in bad gameplay experiences like keeping an enemy alive in order to get the best boosted heal roll possible.