Фрагменты с заметно большим шансом падают с Прорывов бездны, если долго не падает нужное кол-во реликвий можете пойти открывать порталы.
Взято из английских комментариев

Комментарий от eminsk

После сбора в количестве 6 шт., дает Вам Проклятая реликвия

У элитных мобов шанс выпадает всегда выше в зоне видений и может прокнуть больше лута. Чем слабее моб тем меньше падает лута. Шанс у каждого игрока всегда разный еще, кому может падать больше кому-то меньше. В этой игре все рандомно падает и как кому повезет.

EDIT: Based on the recent down votes, this appears to have been fixed.

If you have five relic fragments and can't get the sixth to drop, check your inventory and bank for a different type of relic fragment from a previous assault. It appears that you can only have six Vale relic fragments, even if one is of a different type. This is possible if you kill a group that drops two relic fragments while you are holding five if you loot one (making six), make your relic to open the chest, and THEN LOOT THE SEVENTH FRAGMENT! Don't do that. I discovered this after over 100 kills trying to get the Voidwarped Relic Fragment to drop. I remembered the mogu relic fragment from the previous week, dropped it, and had a Voidwarped Relic Fragment within five kills.

Комментарий от chaostorm

Vale of Eternal Blossoms farming spot: Tu Shen Burial Ground (name is visible from the world map). Послушник Н'Зота have a 25% drop chance, but killing everything in the area gave me all six in less than 8 minutes as an ilvl 459 blood DK. That also just happens to be where one of the chests spawns. Coincidence? Maybe, maybe not.

Комментарий от Eillesthis

These > Проклятая реликвия > Сундук Темной Империи, which requires either Нападение: Темная Империя (Uldum) or Нападение: Темная Империя (Vale)

Комментарий от Mathaylla

Loot tables appear to be messed up in 10.0 pre-patch. I looted all 6 of these in Uldum from a chest and Aqir mobs in Ankhaten Harbor while the Aqir assault was up and I was trying to get aqir relic fragments. There is a Black Empire assault currently happening in the Vale of Eternal Blossoms so possibly that's affecting the loot table for the mobs that are not associated with this type of assault.