What is the point of having BiS

[Raikai]

If you're at ilvl 660, you have gear that will see your adequately through the Dawntrail MSQ until you get your level 100 Job Armor. You won't see better gear until the level 95 dungeon*. The 600 gear and a few dungeon drops will be all you need to get to level 100, you can save all those free gear coffers* for leveling alt-jobs, or selling.

* - of course assuming they follow the same pattern as previous expansions.

Ironically, going into a new expansion with BIS just for the sake of having an easier time became kinda irrelevant with the advent of Duty Support. Granted, you still need a real player party for the Trials (assuming they won't do something like a Hydaelyn duty support again), you can do just fine with whatever gear you find.