1) Stop trying to cater to these "raiders" at the expense of other players. They'll NEVER be satisfied with anything you develop. They only live for the power trip.

2) Consider integrating puzzle elements (e.g. Certain enemy groups must be killed in a certain order or they revive entirely) in each dungeon to slow down speedrunners.

3) Make the current armor rewards in the new dungeons part of a series of upgrade recipes for crafters (iLv for the resulting armor can be 195-200)