The AoE during the Sangoon fight is bugged doing max damage with the protective buff you get from being behind the Tall rock.

This is on Calamity 6 and yes I have all the correct orbs, my dp is 346. I've already cleared Calamity 6 with Sangoon and I come back to see the fight bugged, just like the Gumiho double clone smash.

What the heck is going on? is each boss slowly gaining a bugged area of the fight causing it to not be doable.

Pretty sure thats just an unfortunate case of back attacks proccing and killing you that way. You had the DP buff on your bar, and without it, you would have died much quicker to that AoE. Try again and make sure you use an iframe (your dash) or a SA during the first AoE to avoid being CCed, then you wont have to deal with the chance of getting back attacked.