eh, disagree, you blast through a thousand mobs at a record clip once you're geared and have firewall and icestorm leveled, increasing xp on lower caves trivialises early game content, especially with rebirth etc. on the horizon
can see an argument made for decreasing total xp per level after 40, but nobody that's 45+ currently has moved out of bdd 1 for the past few days other than to pop bosses (myself included), and even without rebirth points, you're still capable of gaining a level or two per day