Ok, this one might be controversial. But i feel like once you max out one class and say you want another, leveling just becomes a chore you try to get through as fast as possible. Which is fine, however personally i find it quite boring the cycle of "just level to lvl 40 as fast as possible then spend the next hours in flesh cave till 85, then scrapyard till max."
This skips through huge areas of the game from level 40-90, like Cinfras, CotL, Molten Heights, Sky Islands, each of which are well designed and fun areas. I feel like the best solution to this would be nerf flesh cave a bit, or make it so the threshold for getting 0 xp is a lot closer to your current level. i.e, flesh cave should serve as a good grind spot for 40-60 ish, after that find some others which work.
It will add an incentive for players on succesive playthroughs to go to other areas of the game too, and not just be in two areas for 90% of it.

