After working with States Machines in several demos/projects, I decided to give a try to another approach for designing AI behavior, know as Behavior Trees.
I was able to find two excellent tutorials by Dominik Hackl : https://www.youtube.com/watch?v=T-zbN1XSQJk and https://www.youtube.com/watch?v=X7VwAGvAOIw
It is not a perfect reproduction of the two fights of the game, but it is not very far off in my opinion.
In my journey to becoming a Game developper, being able reproduce the experience of such an iconic game (which I have played myself) is something special for me.
I will probably continue to use Behavior Trees, especially in this kind of case (boss fight with multiples attacks patterns, and multiples phases).