Using the 1st void ark as an example...

TL : DR
210 dyable void ark gear
higher boss hp
shorter enrage timers
higher incoming damage
failed mechanics = wipe
Only premade alliances can enter
aimed to be bis ex difficulty scaled to 24 man.

This would close the midcore content gap. The fights would be retuned, not redesigned. It would give meaning to grouping up outside of df. A sense of community would return to the end game. etc etc etc