This question reminded me of my own question regarding Octavius Witchblade a while ago and Assassin’s Mark application re: IT damage. I went back to the thread and CrabTurtle answered my question using the exact example of -125% RR you mentioned. So yes to both.
The answer is buried in the thread and spans about four comments (including some from you haha), so here’s the link and the comments you want are about 40 to 45.
Can’t wait for another DeputyChuck DoT monster!