All the drops are random, and some are extremely rare.
However, they aren't bugged as I just helped a guildie 2 days ago get the Hafiz Memory, Ice Fragments, and Cactus Thorn.
Just keep plugging away is what I suggest. It took me 37 Raichka kills to get 1 feather, then I got the second feather on the very next kill.
And I had to kill Hafiz 7 times for the first memory, then another 18 for the second.