Imo the problems of Zafina are :
1.Her fighting style : No one has ever seen a fighting style like that.
2.Her Psychic personality. Imo she should have acted more like an Assassin than just a psychic.("You aren't strong enough to change fate.")
I don't think those are really problems. Zafina is basically the Street Fighter Rose or the Soul Calibur Zasapamel/Viola of the game with how she acts and operates. Her style isn't complex to implement either, it's basically confusion fu but she doesn't have all that much moves anyway, her style is more a style to throw off where the opponent thinks she'll hit. The main issue I think is that Zafina fans are just toxic and like how a mother doesn't buy her a little boy a treat for bad behavior, Harada did that to her fans xD
If I was a game developer, there would be no way on earth I would give a sect of my fans what they want if they threatened my life, anyone who wishes death upon someone or is happy at the thought of someone dying or having died is truly messed up and doesn't deserve anything positive