Prove it, release the debug build, lol.
I think the mace smash sprite make it seem larger than it is and the early hero pattern makes him easy to hit thus giving the illusion that the inflicting damage area is larger in the beginning.
For real it was an amazing experience.
Surprisingly, I beat him without going into phase 2. I cheesed him by standing in place near the throne and spamming spell and mace, the spell forced him to move closer to me and the mace made him move away, if he ends up trapped between the spell and the mace it is guaranteed hit.
Luckily he was not programmed to spam arrow in retaliation, otherwise I would have been cooked.
Also, thanks to your game, I now have the boss perspective and I can see bosses as a sequence of patterns that can be easily dominated one by one. Thus I was able to defeat Lucine after 160+ deaths, 5+ hours over the span of 5+ months.
Phew, this is a lot, but it was a unique experience :)
Edit: Fixed the amount of hours. I read the game time wrong