As it stands, all endgame duties are full party only and are designed to be challenging and award high end gear (extremes/savage) or rare titles and glam (ultimates) dungeons always lag behind in gear because they are designed to bring the player up to a minimum for fresh max level characters and jobs

Currently the only solo content at endgame is your relic, and even though eureka could be done solo up till the arsenal, to even have a chance of completing the max level fates you needed to get in a party anyway.
Thing is the relic isn't hard, its just slow more often than not. There's not really anything to test the player's individual skill at their job that is not a party duty.

In addition, pretty much all solo duties have become jokes now what with options to scale down the difficulty for story players even though at least from the forums, most people found them easy to begin with or view them more as minimum competency barriers (which even then are meaningless given people still stand in aoes repeatedly after the difficulty option pushes you onto easy/very easy)
There's 3 or so fights that require a party in the story each expansion, yet we go from several solo duties (now that we have trust to grab all the gear and dialogue etc) to party ones


So to spice up endgame a little and make things less frustrating for players who play at awkward times or don't have a super high parse for statics, why not bring in solo duties at endgame with appropriate gear? It could even have some added rng and a lockout as needed to ensure someone couldn't just hop in and power boost up to high ilvls

Its already canon that the WOL cleared a lot of climactic battles solo, so for additional story and or settings then these could be revisited- perhaps Lord edmont's memoirs for a framing device