Whats even more dangerous than a blown acl is scrubbing speed at 40+mph is steep rocky terrain and having a ski blowoff.
For me personally, i crank the DIN on my charging skis because ive had a ski blow off which sent me into a high speed ragdoll crash in which i bounced off a rock and sent a 20 footer headfirst backwards. Or had a ski blow off while scrubbing speed in chunder. Or had to wait 2 hours form ski patrol to get my ski because i left it in some super precarious position 200ft above me.
Id rather blow an ACL or break my leg than have the kind of crash that carries a +10% chance of life flight type injury. If i am to get fucked up, id rather it be my fault than that of the equipment. I totally and completely agree with you though, i started at the DIN chart recommended, and as i had pre-releases went up by 0.5 DIN from there. THat is how you have to do it, small increases till its dialed, just hope you don't have a pre-release in a bad situation while trying to find that right DIN haha.
That said, i ride at literally half the DIN on my rock/everyday skis. Id like to bump them up, but the tensioning screws are stripped, so i just make sure im skiing very smoothly and light on my feet a la Hoji. And due to the shit conditions ive had the last 4 years, days spent on these skis are usually poking around, finding cool stuff to ski once a storm finally comes in.