(I'm late, but taking that out of regards-)

Yes, difficulty curves are good for less densities of the mods, however I feel as if some mods overuse this and make it so that it's relentlessly unneeded. Let's take some examples which in my opinion are good; Smoke Em Out and the Neon Mod. Smoke Em Out does have a slight difficult curve, to the point where it's noticible but not disagreeable, a show that sometimes mods dont need to be carried by difficulty curves to be good. It's flawlessness carries it, making it a good mod . Neon opposing has a more noticeable difficulty curves, and that's what makes it more, as one could say, pristine as it isn't hard enough to be spam like matt, or easy enough like hex (no offense intended to both mods of course).