I did it for Raze myself as well but also found all the enemies in his fortress pretty tough at the time too but with some serious updrading in my workshop the other fortresses were very easy. Going up on all resist by 15% and adding 200HP tends to do that. Only other time I thought of doing it was the arena near the end of the game, one particular demon's second appearance had a fireball that could do 862 damage in one hit even on my upgraded character that was level 35 with 742HP and around 60 or above on all resist. Was wild, however as long as you somehow manage to not get hit by that first shot he throws you will likely take him out quick enough that he doesn't get a second chance, still amazing the sudden KOs you get in this game sometimes that just seem to come out of nowhere.
Speaking of the arena, somepeople find that if you use the Shield Charm quest item as the fight starts the bosses there do not one-shot you.
But getting 1 hit by bosses sure makes it tempting to go lower the difficulty many times!