this is a video which i made to adress this issue, if you can , share either the video to cd project red's twitter/ forum or keep posting new threads to influence cd project red to change this. We need a scaling up system. https://www.youtube.com/watch?v=a9WJEsBYKzk
A non-mod suggestion I have is to try not using witcher gear. I know it looks badass and is fun to make but it completely ruins the loot system. If you're not using witcher stuff, the things you pickup are way more likely to actually be usable and of interest. Just something to consider.
As for modding...
Funny thing is, you don't actually need a lot of scaling, just remove the negative scaling that's already in-game. Monsters get a -40% when below your level, getting rid of that makes a huge difference. Then I upgraded the amount of damage they get per level, removed some of Geralt's more busted sources of scaling (mutagens and griffin techniques are the biggest culprits) and the end result is something that is way more satisfying than vanilla imho. A 6-pack of nekkers can take me down if I'm not being tactical and bosses take 2-3 hits to kill me with a non-tank build.
his mod is the first mod that actually did something with the way lower (and higher) level enemies behave, with all the artificial buffs and penalties.
so i recommend looking into his mod as well as mine.
i took cronstintein's values and tweaked them to make lower level enemies hard enough so over leveling isnt a cake walk.
my mod makes the low level enemies much more potent (and there are versions of the mod that make high level monsters easier or just as hard).