Yeah it has quite a bit, actually. I think the value when you are close to death (your last 25% life?) is 25% damage reduction. It’s really noticeable for big one-hit moves like Jago DP or Tusk st.HP.
Ah, well i imagine for some, maybe a good portion of players, the mindset at around 25% life kinda goes to ‘how can i get to my ultra faster’ because i’m blaming that on why i never noticed for myself.
Does this mean aria technically has less health than everyone else since her almost dead point is lower than the rest of the cast meaning scaling kicks in later?
I don’t know if it’s a strict value or a percentage. Aria also probably has guts kick in 3 times rather than 2 times, so I dunno it probably just works itself out?
This thread is actually the first I’ve ever heard of this. I’m curious why it doesn’t get talked about more. In essence, this sort of scaling is just mathematical trickery. You might as well just give everyone more total health. I assume they do this to allow for the kind of hype “hanging on by a thread” that people like to watch, but as far as the overall game it doesn’t actually do anything. - especially in a game like KI where all characters have the same health.
Guts scaling is poor design and always has been, imo. Still, it’s pretty minor in KI and would probably be more trouble than it’s worth to remove it and adjust health values to compensate. It could be a lot worse…health bars in xrd are so, so stupid. 
Im still learning Xrd and Rev 2, but watching the end game of matches, it seems like every character just refuses to die.