Indomitable doesn't count? It's not legendary resistance, but that's reserved for monsters.I don't really worry about the wizard feeling powerful after level 4 (and almost no class feels particularly powerful before 5 anyway, with a possible exception for Moon Druid). I've never seen a high level wizard that didn't feel powerful in play.
What I am concerned about is martials feeling powerful when played. Because I don't think they do. They have staying power, but that's not the same.
If the fighter had a no save instant death ability (even once per day) that would feel powerful.
So they need Hulk or Superman levels of strength? Able to throw tanks like they were frisbees?If they could tear through a porticulis like it were made of paper, that would feel powerful.
Can any class do that? Exactly what kind of power would this be? It's quite situational, but you're talking about what ... super intimidate?If they could single handedly stare down an entire regiment of soldiers and make them back down (without relying on DM fiat) that would feel powerful.
You clearly have a different definition of powerful than I, or people I play with, do. What you're talking about is mythic level/comic book superhero. You want demigods, I want mortals who are fighters of legend but still ultimately mortal. I've played martial types to 20th level and they felt plenty powerful to me.But a 20th level fighter cannot do any of these things.
I agree that your suggestions would make them powerful. I have no idea how you'd balance it out. I also don't see how it would fit D&D.
