I would personally be resistant to approaching any sort of post-level cap XP grind even in a sequel.
Experience is intended to be the progress you accrue towards your character mastering their skill and potential. Seems strange to me that as soon as you hit max that this experience starts going towards loot rewards.
I think I’d rather work in some kind of new system, like rewarding milestones for slaying X monsters or bosses or heroes, or opening chests, etc; although those would probably encourage some negative gameplay experiences like spamming big packs of weak spawns.
The ideal would be having tangible goals that you could work towards and earn rewards, ideally repeatable, that would be conducive to endgame while not just piling on extra rewards for stuff you were doing anyway.