Guild Wars 2

I have been going on making alt after alt, with little thought to what I would do after I hit 80. My characters are:

• 80 Shatter Mesmer [Artificer, Tailor] mostly Rare gear, 100% world completion. I only use this character when I need to go somewhere my other characters lack WPs for (eg during Scarlet Living Story).
• 80 Mace/Focus Guardian [Armorer, Weaponsmith] full Exotic. I have recently begun using this character in Dungeons (most fun I have had with the Guardian), so I will likely keep this focus.
• 80 FT/EG Engineer [Jeweller] mostly Exotic. Enjoy this character more than the Mesmer, but rarely use it.
• 78 Stealth-focused D/D Thief [Huntsman, Leatherworker]. Almost 80, but no current plans for what to do once I get there.
• 31 Ranger [Chef]. Currently no plans to play again :P
• 11 Necro. Intend to level after finishing Thief.

I intend to use the Guardian as my primary Dungeon character, and probably nothing else. I have no idea what to do with the others. Any suggestions to what areas of the game they would be most useful for?

I have 9 level 80s. I keep them all parked in Frostgorge and hit the ori and ancient wood nodes daily. Or you can keep each one parked at a chest and open it daily to get empyreal fragments.