The leap between Mount Olympus and Astral Plane is punishing and literally takes months of real-world persistent farming (even if going 100b a day, with Crazy Tapper, multiple transposes). This is further elongated by the reality that there are multiple people farming Zeus as the best source of XP, and only two Zeus' at a time (which is a massive improvement over there being only one).
I propose that after receiving the 1k Zeus Shard Triumph, you unlock a Zeus-Only area, or something like that, that is a stepping stone between Mount Olympus and Astral Plane, to help a bit with the grind to Onyx. It doesn't lessen the requirements, but gives you a more reliable source of XP. As it stands right now, burnout is very possible due largely to the scarcity of Zeus' for XP each day.