From what I understand, a breakthrough salvia experience is about as intense as you can get, for most people it seems to involve a lot of fear though, with awe and amazement afterwards. Almost universally people report suddenly becoming utterly aware they did a drug and not remembering anything from before the effects, and the effects... well, read the trip reports on Erowid, they're fucking wild. Personally I've never broken through on salvia.
Yes I experienced this once, in 2004. Smoking a ×15 salvia bucket bong, after some ketamine, on mushrooms at the end of a 15 ecstasy pill weekend binge.
It was crazy, and the single most terrifying experience I ever had in this life where I was convinced eventually after being whipped around through different rooms and palaces and castles etc hallucinating my friends plotting against me and leaving my Reality trapping me behind until I was convinced I had been buried under concrete tricked by demon at a rave party which we failed to attend that Sunday night.
It all happened so fast and was a brilliantly fascinating, exciting and terrifying all at once full-blown hallucination slideshow. Then immediately I snapped out of it and was back in the room 100% myself and feeling really amazing to know that I was actually alive and none of that was real.
I mean it was the most god awful frightening thing ever at the time and I didn't know what was happening or anything like who I was where I was all that I was even on a drug.
But it left me with not only zero trauma but actually the opposite effect and a remarkable appreciation for life and sense of well-being and peace and happiness.
I agree that Salvia is about as intense and hardcore as It gets I haven't done DMT but I'm actually not intimidated by it but I am intimidated by salvia.
I even found low doses difficult.
Also, you can kind of get a feeling for how hardcore it is by the way that Terrence Mckenna speaks about and regards it. Like equally potent as DMT at least.