We've done all the Hero's, almost all of the partisans/mercs (ones that are available in game), we've done some serious grind sessions and we've been at it 14 hours. We have seen 5 of these diamonds.
I've gotten 11 so far in far less killing, only having dabbled in CC and Rygorr Mines so far with no missions/questing done - just exploring really. Maybe certain mob types have a better shot than others, can say the Rygorr have a supply of them (still rather uncommon).
I've got about 7 of them. Done GD partisan(twice)/merc and the group missions. Not any real random killing/grinding other than when I did an oops and let invis drop. Your luck is either horrible, or you're killing some sort of mob type that doesn't drop them.
To elaborate from my original post: All of the GD mercenaries/partisan and Hero’s, the EW Hero’s, some of EW merc/partisan (what was available), all of Ry’Gorr and CC questing, Kael Hero and Velk’s Hero, plus flagging 6 people for the second floor of ToFS. The missions we did 2 times each for coin. There was a lot of killing and reclearing etc in CC and a lot in ToFS floor 1 for 6 keys. All of that killing resulted in a grand total of 5 for the GROUP.... Now on day 2 I went to Kael for partisan/merc and we killed in 1 area for about 4ish hours and we saw many more diamonds ...I’ll have to check parser when I get home from work, but maybe 15-20? Still seems quite low and considering both the JC and research that require them, the drop rate still seems lower and maybe not on enough of the mob types. On another note I saw those god forsaken stone of tranquility are still on the loot table despite Ngreth, I think, saying he’d remove those from the drop table of anything over X level....
