Can't say I'm a fan of random drops, dungeons are boring content all around (that's not to say we shouldn't have them though), to add rare gear into them will force people to run content they don't to do over and over. They've made that mistake with the Diadem, no need to repeat it a second time. I do think we should get gear set bonuses though, and interesting ones, not just "6/6, 50 Critical Hit Rate bonus" but rather "6/6, Dream Within a Dream has a 5% to proc after the execution of a mudra, immediately resetting its cooldown". Now, that would likely be a nightmare to balance but it would bring some life back into gear.