You can definitely make the content harder to heal but accessible to new players, especially once they've gotten to SB. At that point they should be pretty familiar with their class. It doesn't even need to be just throwing in bigger numbers, you can put mini-mechanics in the dungeon itself or give the trash mobs some tricks up their sleeves. The last time I had trouble in a dungeon was Baelsar's Wall after coming off of a 2 week break and was a bit behind gear-wise and even then it was just the very first couple pulls I was having trouble with (but I did appreciate the enemy bards throwing venom/windbite on party members. It wiped each of my parties when pulling both encounters but it's def the kind of stuff I want to see more of). After that it was laughably easy.
For example, there's no reason that in Sohm Al Hard I should go in as SCH and almost never leave Cleric Stance, even at i267. Selene should not be able to keep the party alive by herself, in boss fights especially. At that point it's too little damage.