Whole leveling thing is just too much over the top.
I just did playthrough with 30perc slower leveling mod. Coupled with potd difficulty changes, this was quite hardcore, for some major fights you were just properly level starved (in a good sense). Seems some mobs are now even higher level than before, making it real fun.
I cant recommend this enough. I reached lvl 20, still havent done scriveners, bekarna, and that corpse island + ofcourse ukaizo. Not even talking about DLCs.
Point is - with vanilla leveling - playing more than 1/3 of game level capped, is bit boring, at first - level scaling upwards is limited, so it lowers chalenge, and also - no progress in rpg, seriously???
It could be done at least as challenge (totally not fan of those), or as part of potd difficulty. Flat 30 perc is about perfect (for wannabe completionist run, but i still missed/messed quite a bit of quests).
I understand that for causal player it would be problem, but those wont go for highest difficulty (or challenge). Or there could be implemented some kind of intelligent exp scaling.