The way I use to get raw diamonds in PoJ, because they are so common, and I can sell em for 200+ pp each, I roam the halls by the exit out looking for Sentries of Justice and Gaolers of Justice, they're very easy once they are slowed, but you also want to snare them because they do run like wussies once you get them down to 20%. You don't want extra adds killing you. Raw Diamonds are pretty common.
Other ones are the enforcers down by Muavin. Once you get past the High Guardian of Justice ( Which is indifferent ) You get the the enforcers, there's a punisher before them, but after that... it's just enforcers. Now when you get to the first hall, lull one on the side and pull one on the other side, keep doing this till you cleared them, Same with the big hall and if you get any trouble... fade! Both the Sentries of Justice and Gaolers of Justice and these drop these diamonds a good ammount. ( Like 10 - 15 Every hour I believe ) Enforcers aren't immune to anything, snare, root, lull, mezz, nothing. They hit around 150 - 200 kinda fast, but once they're slowed you can play around a little more... also they flurry. But, if you bring some healing potions, this is cake for all you [b]Level 65+ Bards[/b]. Yes, 65+... this isn't really a 50's bard thing to do unless you want whooped :D