Vashj and Kael should drop only 4 vials before patch 2.1 for the Hyjal attunement quest.

"The drops for "The Vials of Eternity" have been modified. Vashj's and Kael's Vial Remnants are now multi-drop quest items. This means they'll be lootable by each raid member who is on the quest, as opposed to the four vials that drop at the moment."

http://eu.battle.net/wow/en/game/patch-notes/2-1-0
https://mods.curse.com/news/world-of-warcraft/3510-ptr-patch-2-1-notes-download-mirror

"When Lady Vashj was first downed by Nihilum, four and a half years ago at the time of posting, she only dropped 4 vials of eternity, which would have meant 7 kills before you got to take a full group to Hyjal. Unsurprisingly, given how hard this encounter was, that restriction was lifted almost immediately and the vial was lootable by all."

http://www.wowhead.com/quest=13432/the-vials-of-eternity