I would go with my friends and work on getting pop item drops while they did staggers. I often played on BST. Rewards were plentiful enough that it was no biggie having friends along even if they weren't perfect, and BST had strengths in absysea, it was no where near as far behind as it is now. No one is going to want me on BST for delve.
Also I am not calling for the items to be 120, I am calling for the items to be as good as delve items or slightly better in some cases - but at 119. The game used to have good options for almost every slot for almost every job from almost every event. That made it worthwhile to do more than just 1 event.
Why wouldn't you want that? hardcores are all capped out on delve already and casuals never get to do it, so I don't see the point in keeping most of the best in slot in that event.