Despite being an old topic, there is little information available on the internet, so maybe this will help someone.
I did a simple test by multiplying the final formula by 100 and it worked well. However this was just a test and I recommend playing between 2x~4x not to get too far from the level of other monsters.
To make it easier, download a "mod" with pre-formulated map, otherwise you'll need to create one in the editor. You will also need ARZExplorer to extract the files if they are compressed and ArtManager to edit the formula, you can even use Notepad++, but you will need to recompile with ArtManager.
records/game/gameengine.dbr (Change directly in xpack folder)
xpack/records/game/gameengine.dbr
experienceEquation,(((monsterLevel*15)+((monsterLevel-averagePlayerLevel)*(averagePlayerLevel/3.5)))*(1+(monsterExperience/100)))*100,
Usually other users multiply by 5, 7 or 10 and it improves a lot.