Anything past tier 5 or so will drop rares and uniques at a decent enough ilvl to be good.
Mapping isn't very profitable compared to other content in the game, though. The main reward at higher tiers is better XP gain. But since pure breachstones are a thing, even that's less important now.
This is why exalts are so expensive now btw. People aren't sinking chaos into maps, either for rolling or for extra league mods.