I will advocate for Dark Miasma, Trick Arrow, Cold Domination (sorta unplayed) and it's brother Thermal Radiation for underrated Defender sets.
As mentioned, power creep ate all the buffs. Also as mentioned the above sets are phenomenal debuffers with their own niche. Dark and Cold bring a bag of tricks to the table as well as their own thing. Dark is better when things get messy, able to flip an encounter from a wipe to a win with Howling Twilight alone. Cold is that one guy who dumps a tray of ice cubs down the back of your shirt but instead does that to AVs. Both are good at shoring up defenses if you have people below the cap. Trick Arrow takes the bag of tricks mentioned above and trades it in for a dump truck of tricks. There is very little on the debuff end Trick Arrow can't do, the set is merely unpopular due to the high skill floor but I have seen good TA players and they are scary people. Thermal is my personal favorite for flavor reasons. It's a bit of a mixed bag like Dark. A few heals, a few buffs, and the two big ones: resist shields and melt armor. The resist shields sound useless I'm sure, but they aren't. With everyone capping defense having resists keeps you from getting oneshot when they do actually manage to hit you. Melt Armor is exactly what it says on the tin, an AoE defense and resist shred. I had a friend who is waaay better at builds then me find out it can actually be near-perma'd in a full recharge build.