I'd certainly leave Tellah's death as it was. I'm not sure if I'd call his death a 'villains death' because despite wanting revenge, I think he was doing it for justifiable purposes. Although they are unrealistic, I don't think I'd change them. Perhaps moderating them slightly like KoShiatar suggested above would be more realistic and bearable, but I think that the characters inability to die in FFIV is something that I equate to FFIV in much the same way as I equate bad Engrish to FFVII and the word "whatever" to FFVIII.