More class specific interactions would be fun. Giving rogues chances of detecting/evading traps, unlocking doors (bring back lootboxes).
Shamans doing totem/elemental things in the open world (totem acquisition quests, RIP)
Priests/Paladins out doing their daily devotionals and curing plagues.
Etc etc etc.
Im here for the combat and i dont do delves, but i feel like things of this sort could be expanded upon in delves to make them more fun and individualized on a class/spec level than simply a one size fits all
Gives more open world interactions too for those who enjoy that.
Could open the door for more interactions in potential challenge modes for those who prefer things with a bit more bite