I think that intent is fine, but being hard to hit, and the last boss being hard to jump over too makes it a bit frustrating as a player. The other ones are also hard to hit, but you can leap over them and continue trying. On the third boss, I was thinking of it as a timer in which I needed to hit it until it died before it could reach me (A demon wall from final fantasy basically) and once I couldn't hit it more than twice before it reached me, I just gave up.
Facing difficult gameplay isn't an issue, but being sandwiched by difficult gameplay is draining.