I wouldnt think of those wacky mechanics first.

I'm more nostalgic about things like enemy healers (guildhests), enemies getting damage stacks that you have to manage, adds doing specialized things, enemies you have to balance and keep alive or kill, etc. Best examples are T1, Melusine, Caduceus, Imdugud, Quickthinks Althoughts, Sirius Hard, or even old Gyascutus(Aery) and Raskovnik(Sohm al) that unfortunately were too undertuned for their actual mechanics to shine and be noticeable. And then you also had Leviathan that actually limited healing with that infamous briny debuff.

I also do miss bosses like that have soft enrage mechanics not based on damage stacks or buffs, but that simply blanket the room with more and more AoEs until you cannot survive it, like the Leightonward (Sohm Al hard) or Deathwing Hollow. I like the feel of impending doom they bring, and even ShB had Therion doing exactly this as well.

Personally I want more RPG mechanics and less DDR mechanics.