I am strong enough to clear 300 corruption echos without breaking a sweat but I have to start every timeline at corruption 100, clearing 20-30 echos to get to 200 corruption without any challenge whatsoever. All I do is speed through the echos and constantly press 1. No brain is needed and loot is terrible.
The Harbinger questline in particular reveals this downside of the current system even more, I cannot focus on the timeline I’m interested in and just level that, no I have to clear all timelines starting at 100, even if the special reward does not interest me.
The simplest solution would be some way to increase all timelines to 200 with a single quest but keeping the current reward structure. Think D4 capstone dungeon or some difficult boss encounter. If you clear it, all timelines will be 200 instantly. There could be several more quests/dungeons to increase all corruption even further, the sky (and your personal build/skill) is the limit.
Please, this (and the cumbersom campaign skip mechanic) is the single reason why I have no fun creating alts. Every single time I have to go through a period where LE is a pure running simulator, completely unrewarding and only timewasting, until I get to the fun part again.