The problem is FFXI is a dying game, this is not WoW with 10 millions of active players or FFXIV with 500k. FFXI hardly have 30k active players between all the servers.
Square enix create the trusts to allow us solo content cuz the game lack of players.
For play OMEN you need have a GEO, COR, BRD or WHM if you want to use a DD class you need an AG-WEAPON.
For play Escha again you need people you can't solo escha with Trusts unless you are godly geared and with all vorseals unlocked
Ambuscade is for excellence the CASUAL content for returning players. If the Dev team remove the rewards or do a stupidy they will lose more than WIN.
Also FFXI in my opinion is not anymore a MMRPG is more like PSO, PSU or PSO2 a "ONLINE-RPG" 95% of the content can cleared with 6 man.