So, I've just figured out that if you want to hunt those treasure dungos with the rare weapons, you should not eat up all the red blobs to provoke a fight; they never spawn from them. Instead you're supposed to run through the dungeon and wait for the fights start on you. Really good to know, because I almost never got any of them until recently, since starting fights on your own has its own advantages and it also resets the encounter counter/bar such that you're in control of the thing. Anyways. Now that I know, I've seen them quite a bit already. I think the same applies to the rock crystal. On the other hand, the lucky experience bunny only occurs in fights you started on a red blob.
Best dungeon so far to easily farm/upgrade rares for me is Malgrid 6, btw. Southern route, almost no fights, and plenty of chests. But it drives me nuts since it's so repetitive (just rerolled the decapitation blade a shitload of times, ugh).
What are you favorite rares anyways? And who do you give them to? Some are rather odd too, for example the Buddha staff offers magic and almost as much attack (magic=400, atk=330, speed=10, body boost=10%, and Talent R). Now what kind of sorcerer can use attack? The only char I can think of is Mill Yorks with her Eidolon attack, that's physical, right?