Blizzard removed a lot of the reputation requirements and it becomes obvious that the conditions for the quests that fulfill this achievement are not in the best shape.
I therefore created #27 and hope to be able to figure this one out
Grail.lua.txt

The whole thing starts to go south with http://www.wowhead.com/quest=43309/the-perfect-opportunity
Nightfallen Rep is ok , but Arcane Thirst doesn't seem to be properly tracked.
Thalyssra is topped up with arcane mana, but the condition is still red.
Also 21/100 is considered "stable" but not in Grail&Wholly.

#25 has the details