Frizze covered most of it. The real value of omni-crafting/gather (all DoH and DoL at 70) is self-sufficiency. As SE adds new legendary gathering nodes, they also increase the requirements needed to use the gathering nodes. Which means new gear. This cycle happens on nearly every major patch. e.g. 4.0 Serge/Twinsilk gear, 4.2 Ala Mhigan gear, 4.3 Onishi gear.
This game is pure vertical gear progression treadmill and that will not change.

An omni-crafter/gatherer can get all the materials and make the gear them-self. A solo has to be at the whim of the market board or have an omni-friend/patron.