JoH difficulty really feels out of whack. My knight enchanter, with Dorian, was using barriers like usual at lvl 24. Didn't have any problems with the dlc enemies. Even took down the group of lvl 30 despair demons. Gurd, what a joke. Hakkon, what a joke.
Then did it with my lvl 27 rogue party and the dmg was way way higher. Archers would drop the teams guard in one or two shots, constantly freeze them even with 50% frosty protection. I didn't have any ranged defense and I didn't feel like creating another set of armors for it. The archers took a few shots and everybody would be dead. Champion Hakkonites were only annoying if I got caught in their smash cycle. The regular melee & mage Hakkonites were no problem. Instead of constantly spamming health potions I started dodging all over to get into range and then let my hidden blades take care of everything. I know I could've used stealth but didn't want to, been doing that the whole playthrough just because 
Tried to take on the lvl 30 despair demons but their barrier was out of this world strong I just abandoned that idea.
Took a few tries but I did manage to take down four pride demons. That electric damage was also really strong. Dodge, dip, dive and dodge was the best tactic for them too.
Gurd was no problem once I realized he kept getting infinite minions I just focused everyone on him and down he went fast.
Hakkon was really easy. Hardly did any damage at all. His melee attacks easily absorbed by everyone's guard and kept the team moving behind him to avoid ice breaths. I actually had to kill him 3 times beacuse the game kept crashing in the final cutscene and then I just skipped it the third time. Don't know why, my mage didn't have that problem.
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Both of these teams did it on normal.
lvl 24 KE hardly noticed anything different from the vanilla game.
lvl 27 rogue party felt close to playing a lvl 1 on nightmare.
The difficulty scaling feels like someone put random numbers into it. I don't mind the damage output / increased enemy health. But the way the stats seem to work is that they don't really work. Barrier is the new health spam from previous games, and guard is fine for melee but anything with strong armor penetration or magic is just gonna tear through guard insanely fast. And I always feel like the defense stats on my gear doesn't really do anything. A lot of pure armor value will absorb pretty much anything if you get it high enough but all the elemental res and so forth never feel like they actually help at all.
I don't know. Maybe it's bugged, or Bioware still can't get their hands around combat systems properly.
I haven't played the Descent dlc so I can't compare the two.