Having given up on counting on the Devs to make events Fun (i.e. playing their game enough to understand the line between Challenge and Chore), I have gone in a different direction in Bounty to try and reduce Frustration/Timesink, assuming we buy up to Mythic tier in Shop (which I was doing anyway):
As it stands, I need 43 lvl 20 runs to clear all rewards, with 25 sigils to go. Since it took me 7 sigils to clear 19 levels, it should be doable and faster unless RNG unleashes the hate.
This is of course assuming one only cares about the rewards, not the Leaderboard.