That's likely how was implemented in Divinity Original Sin, but I don't like that kind of difficulty scale, because it's either feels too difficult (even on "easy") or too easy even on hard.
There has to be specific options to tweak each separately. Otherwise can't be custom fit to how everyone likes: some want just more or less of the things that bothers them, rest can stay as it is.
To make it easier, I would give myself (and party) far more health, maybe money if there's any use of it, extreme bonus on persuasion and not much else, but wouldn't lower enemy stats ever or make the AI act dumb, because that won't feel easy but boring and dumb game. I want them to fight back properly, even if they won't be able to win because I made it "easy".
To make it difficult I would lower some of my stats, again not touching the NPC and AI at all. You can lower your stats so much that will be impossible nightmare to play it, if that's the target, without increasing NPC stats at all.
This way is the easiest as well, since only your stats needs edited, and the NPC AI can be made and kept as smart and efficient as possible.
