Some of my favorite content ever is the raids inside field ops like Castrum Lacus Litore. You get rewarded with extra chests if you are fast enough to save more prisoners. I like this idea of making it fairy easy to pass but rewarding more skillful play. Adrammalech is also a super fun boss, just the right amount of challenge when it starts combining mechanics like knockback + aoe + pyretic. Things like this and Baldesion Arsenal feel like true raids and are some of the greatest instanced content in the game imo but there's only a few and they are completely unsupported by roulettes.