Well, we sure don't know much about Rayleigh and Mihawk.
Zoro has similarities with both but he is also unique in many aspects of his personality. I believe he resembles more Rayleigh in his role in the crew.
there is no variation really, he just pulled that badass feat every time he's about to win the battle,
there is no change at all in his fight its quite a bummer considering this guy is supposed to take on the 2nd strongest enemy in the arc,
you're the one misunderstand this, I've always talked about his fighting pattern and how he overused that badassery to the point of its not badass anymore.
Hm, I think you fail to see Zoro's growth both in character and in battle style.
Zoro began as the badass guy who thought that was stronger than everybody but very soon he change his attitude during battle. He's one of the few characters that I've seen growing so much during a battle, like in Alabasta against Daz Bones and apart from the badassery part Zoro is very calm and determined in fights, he knows when to use raw power and when to control his strength to achieve his goal (like against Monet).
Also, he has a variety of moves and ways of using them. It's true that he has some main characteristics that appear often, but this goes for all the Strawhats. However, Zoro is one of the few who changes his personality during a fight to gain knowledge or to accept a situation that cannot be changed and behave accordingly.